mint-adjust.py should only add non null entries to array_preserves

[J G Miller]

DISTRIB_CODENAME=rosa
DISTRIB_DESCRIPTION="Linux Mint 17.3 Rosa"

Package: mintsystem
Maintainer: Clement Lefebvre <email address hidden>
Architecture: all
Version: 8.1.6
Filename: pool/main/m/mintsystem/mintsystem_7.9.7+1_all.deb

mint-adjust.py creates an arry of filename "preserves" which are files not to be subjected to mint-update overwrites.

            if extension == ".preserve":
                filehandle = open(adjustment_directory + "/" + filename)
                for line in filehandle:
                    line = line.strip()
                    array_preserves.append(line)
                filehandle.close()

If the line is blank, because the preserve file contains a trailing blank line just like all the overwrite files do, then a null string is inserted into the array. This can result in numerous null entries in the preserves array which is not a good thing, so a test should be done that the entry is non-null before insertion.

                for line in filehandle:
                    line = line.strip()
                    if (line):
                        array_preserves.append(line)
                filehandle.close()