Bug 156844 - 'use of uninitialized value in string eq' warning

r=jouni x2

webtools/bugzilla/process_bug.cgi

@@ -930,6 +930,8 @@ foreach my $id (@idlist) {
     my %oldhash;
     my $i = 0;
     foreach my $col (@::log_columns) {
+        # Consider NULL db entries to be equivalent to the empty string
+        $oldvalues[$i] ||= '';
         $oldhash{$col} = $oldvalues[$i];
         if (exists $::FORM{$col}) {
             CheckCanChangeField($col, $id, $oldvalues[$i], $::FORM{$col});