Fix for bug 92713, show_activity.pl displays zeros as non-breaking spaces.

CGI.pl

@@ -1157,8 +1157,8 @@ sub DumpBugActivity {
         my ($field,$when,$removed,$added,$who) = (@row);
         $removed = html_quote($removed);
         $added = html_quote($added);
-        $removed ||= " ";
-        $added ||= " ";
+        $removed = " " if $removed eq "";
+        $added = " " if $added eq "";
         print "<tr>\n";
         print "<td>$who</td>\n";
         print "<td>$field</td>\n";