I tested the patch, and seems it works as expected.

#old version, reproduce bug

hostname:~/logrotate# for i in `seq 1 100000` ; do echo some entry $i >> /tmp/some.log; done 

hostname:~/logrotate# cat /tmp/some.conf 
/tmp/some.log
{
 rotate 4
 weekly
 size 10
 missingok
 notifempty
 compress
 delaycompress
 sharedscripts
 postrotate
  reload rsyslog >/dev/null 2>&1 || true
 endscript
}

hostname:~/logrotate# ./logrotate -d /tmp/some.conf ; echo $?
reading config file /tmp/some.conf

Handling 1 logs

rotating pattern: /tmp/some.log
 10 bytes (4 rotations)
empty log files are not rotated, old logs are removed
considering log /tmp/some.log
  log needs rotating
rotating log /tmp/some.log, log->rotateCount is 4
dateext suffix '-20150317'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
previous log /tmp/some.log.1 does not exist
renaming /tmp/some.log.4.gz to /tmp/some.log.5.gz (rotatecount 4, logstart 1, i 4), 
renaming /tmp/some.log.3.gz to /tmp/some.log.4.gz (rotatecount 4, logstart 1, i 3), 
renaming /tmp/some.log.2.gz to /tmp/some.log.3.gz (rotatecount 4, logstart 1, i 2), 
renaming /tmp/some.log.1.gz to /tmp/some.log.2.gz (rotatecount 4, logstart 1, i 1), 
renaming /tmp/some.log.0.gz to /tmp/some.log.1.gz (rotatecount 4, logstart 1, i 0), 
renaming /tmp/some.log to /tmp/some.log.1
running postrotate script
running script with arg /tmp/some.log
: "
  reload rsyslog >/dev/null 2>&1 || true
"
removing old log /tmp/some.log.5.gz
error: error opening /tmp/some.log.5.gz: No such file or directory
1

hostname:~/logrotate# ./logrotate -v /tmp/some.conf ; echo $?
reading config file /tmp/some.conf

Handling 1 logs

rotating pattern: /tmp/some.log
 10 bytes (4 rotations)
empty log files are not rotated, old logs are removed
considering log /tmp/some.log
  log needs rotating
rotating log /tmp/some.log, log->rotateCount is 4
dateext suffix '-20150317'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
previous log /tmp/some.log.1 does not exist
renaming /tmp/some.log.4.gz to /tmp/some.log.5.gz (rotatecount 4, logstart 1, i 4), 
old log /tmp/some.log.4.gz does not exist
renaming /tmp/some.log.3.gz to /tmp/some.log.4.gz (rotatecount 4, logstart 1, i 3), 
old log /tmp/some.log.3.gz does not exist
renaming /tmp/some.log.2.gz to /tmp/some.log.3.gz (rotatecount 4, logstart 1, i 2), 
old log /tmp/some.log.2.gz does not exist
renaming /tmp/some.log.1.gz to /tmp/some.log.2.gz (rotatecount 4, logstart 1, i 1), 
old log /tmp/some.log.1.gz does not exist
renaming /tmp/some.log.0.gz to /tmp/some.log.1.gz (rotatecount 4, logstart 1, i 0), 
old log /tmp/some.log.0.gz does not exist
log /tmp/some.log.5.gz doesn't exist -- won't try to dispose of it
renaming /tmp/some.log to /tmp/some.log.1
running postrotate script
0


# after applying patch, compile new version and check

hostname:~/logrotate# ./configure 
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... no
checking for mawk... mawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking whether gcc understands -c and -o together... yes
checking for style of include used by make... GNU
checking dependency style of gcc... gcc3
checking for gcc option to accept ISO C99... -std=gnu99
checking for gcc -std=gnu99 option to accept ISO Standard C... (cached) -std=gnu99
checking for poptParseArgvString in -lpopt... yes
checking for getfscreatecon_raw in -lselinux... no
checking for acl_get_file in -lacl... no
checking for strptime... yes
checking for qsort... yes
checking for fork... yes
checking for vfork... yes
checking for madvise... yes
checking that generated files are newer than configure... done
configure: creating ./config.status
config.status: creating Makefile
config.status: creating test/Makefile
config.status: executing depfiles commands
hostname:~/logrotate# make clean
Making clean in test
make[1]: Entering directory `/root/logrotate/test'
make[1]: Nothing to be done for `clean'.
make[1]: Leaving directory `/root/logrotate/test'
make[1]: Entering directory `/root/logrotate'
test -z "logrotate" || rm -f logrotate
rm -f *.o
make[1]: Leaving directory `/root/logrotate'
hostname:~/logrotate# make
Making all in test
make[1]: Entering directory `/root/logrotate/test'
make[1]: Nothing to be done for `all'.
make[1]: Leaving directory `/root/logrotate/test'
make[1]: Entering directory `/root/logrotate'
gcc -std=gnu99 -DPACKAGE_NAME=\"logrotate\" -DPACKAGE_TARNAME=\"logrotate\" -DPACKAGE_VERSION=\"3.8.9\" -DPACKAGE_STRING=\"logrotate\ 3.8.9\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPACKAGE=\"logrotate\" -DVERSION=\"3.8.9\" -D_GNU_SOURCE=1 -DHAVE_LIBPOPT=1 -DHAVE_STRPTIME=1 -DHAVE_QSORT=1 -DHAVE_FORK=1 -DHAVE_VFORK=1 -DHAVE_MADVISE=1 -I.    -Wall -Werror -g -O2 -MT logrotate.o -MD -MP -MF .deps/logrotate.Tpo -c -o logrotate.o logrotate.c
mv -f .deps/logrotate.Tpo .deps/logrotate.Po
gcc -std=gnu99 -DPACKAGE_NAME=\"logrotate\" -DPACKAGE_TARNAME=\"logrotate\" -DPACKAGE_VERSION=\"3.8.9\" -DPACKAGE_STRING=\"logrotate\ 3.8.9\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPACKAGE=\"logrotate\" -DVERSION=\"3.8.9\" -D_GNU_SOURCE=1 -DHAVE_LIBPOPT=1 -DHAVE_STRPTIME=1 -DHAVE_QSORT=1 -DHAVE_FORK=1 -DHAVE_VFORK=1 -DHAVE_MADVISE=1 -I.    -Wall -Werror -g -O2 -MT log.o -MD -MP -MF .deps/log.Tpo -c -o log.o log.c
mv -f .deps/log.Tpo .deps/log.Po
gcc -std=gnu99 -DPACKAGE_NAME=\"logrotate\" -DPACKAGE_TARNAME=\"logrotate\" -DPACKAGE_VERSION=\"3.8.9\" -DPACKAGE_STRING=\"logrotate\ 3.8.9\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPACKAGE=\"logrotate\" -DVERSION=\"3.8.9\" -D_GNU_SOURCE=1 -DHAVE_LIBPOPT=1 -DHAVE_STRPTIME=1 -DHAVE_QSORT=1 -DHAVE_FORK=1 -DHAVE_VFORK=1 -DHAVE_MADVISE=1 -I.    -Wall -Werror -g -O2 -MT config.o -MD -MP -MF .deps/config.Tpo -c -o config.o config.c
mv -f .deps/config.Tpo .deps/config.Po
gcc -std=gnu99 -DPACKAGE_NAME=\"logrotate\" -DPACKAGE_TARNAME=\"logrotate\" -DPACKAGE_VERSION=\"3.8.9\" -DPACKAGE_STRING=\"logrotate\ 3.8.9\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPACKAGE=\"logrotate\" -DVERSION=\"3.8.9\" -D_GNU_SOURCE=1 -DHAVE_LIBPOPT=1 -DHAVE_STRPTIME=1 -DHAVE_QSORT=1 -DHAVE_FORK=1 -DHAVE_VFORK=1 -DHAVE_MADVISE=1 -I.    -Wall -Werror -g -O2 -MT basenames.o -MD -MP -MF .deps/basenames.Tpo -c -o basenames.o basenames.c
mv -f .deps/basenames.Tpo .deps/basenames.Po
gcc -std=gnu99 -Wall -Werror -g -O2   -o logrotate logrotate.o log.o config.o basenames.o  -lpopt 
make[1]: Leaving directory `/root/logrotate'

hostname:~/logrotate# for i in `seq 1 100000` ; do echo some entry $i >> /tmp/some.log; done

hostname:~/logrotate# ./logrotate -d /tmp/some.conf ; echo $?
reading config file /tmp/some.conf

Handling 1 logs

rotating pattern: /tmp/some.log
 10 bytes (4 rotations)
empty log files are not rotated, old logs are removed
considering log /tmp/some.log
  log needs rotating
rotating log /tmp/some.log, log->rotateCount is 4
dateext suffix '-20150317'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
compressing log with: /bin/gzip
renaming /tmp/some.log.4.gz to /tmp/some.log.5.gz (rotatecount 4, logstart 1, i 4), 
renaming /tmp/some.log.3.gz to /tmp/some.log.4.gz (rotatecount 4, logstart 1, i 3), 
renaming /tmp/some.log.2.gz to /tmp/some.log.3.gz (rotatecount 4, logstart 1, i 2), 
renaming /tmp/some.log.1.gz to /tmp/some.log.2.gz (rotatecount 4, logstart 1, i 1), 
renaming /tmp/some.log.0.gz to /tmp/some.log.1.gz (rotatecount 4, logstart 1, i 0), 
log /tmp/some.log.5.gz doesn't exist -- won't try to dispose of it
renaming /tmp/some.log to /tmp/some.log.1
running postrotate script
running script with arg /tmp/some.log
: "
  reload rsyslog >/dev/null 2>&1 || true
"
0

hostname:~/logrotate# ./logrotate -v /tmp/some.conf ; echo $?
reading config file /tmp/some.conf

Handling 1 logs

rotating pattern: /tmp/some.log
 10 bytes (4 rotations)
empty log files are not rotated, old logs are removed
considering log /tmp/some.log
  log needs rotating
rotating log /tmp/some.log, log->rotateCount is 4
dateext suffix '-20150317'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
compressing log with: /bin/gzip
renaming /tmp/some.log.4.gz to /tmp/some.log.5.gz (rotatecount 4, logstart 1, i 4), 
old log /tmp/some.log.4.gz does not exist
renaming /tmp/some.log.3.gz to /tmp/some.log.4.gz (rotatecount 4, logstart 1, i 3), 
old log /tmp/some.log.3.gz does not exist
renaming /tmp/some.log.2.gz to /tmp/some.log.3.gz (rotatecount 4, logstart 1, i 2), 
old log /tmp/some.log.2.gz does not exist
renaming /tmp/some.log.1.gz to /tmp/some.log.2.gz (rotatecount 4, logstart 1, i 1), 
renaming /tmp/some.log.0.gz to /tmp/some.log.1.gz (rotatecount 4, logstart 1, i 0), 
old log /tmp/some.log.0.gz does not exist
log /tmp/some.log.5.gz doesn't exist -- won't try to dispose of it
renaming /tmp/some.log to /tmp/some.log.1
running postrotate script
0