Bug 13028: Resolve uninitialized value in string eq at cmp_sysprefs.pl line 194

Bug 13028: Resolve uninitialized value in string eq at cmp_sysprefs.pl line 194

If you use the restore option with a partial pref file not containing a version, you will have this error. Also the count of updated prefs will be one too high.

This is corrected by a better test of the hash value in the CheckVersionPref subroutine.

Test plan:
[1] Create a small pref file and remove the version pref (if present). You
could for instance do a pref backup and remove most lines.
[2] Use the restore option with and without this patch.
    So, something like:
        maintclone/misc/maintenance/cmp_sysprefs.pl -c r -f 9999crucial.pref
[3] Check on the error message and the pref count.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>