Comment 2 for bug 1155532

StacktraceTop:
 ~basic_string (this=0x7fff66e136e0, __in_chrg=<optimized out>) at /usr/include/c++/4.7/bits/basic_string.h:536
 pkgProblemResolver::DoUpgrade (this=0x7fff66e13710, Pkg=<incomplete type>) at algorithms.cc:730
 __GI___libc_malloc (bytes=0) at malloc.c:2859
 ?? ()
 ?? ()