fix: address review feedback for tag filter handling

- Add IS NOT operator check alongside != in PHP FilterTerm.php
  (was already handled in Perl but missing from PHP)
- Add defined() guard on $term->{val} in Perl Filter.pm to avoid
  uninitialized value warnings with malformed/legacy saved filters

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pliablepixels

scripts/ZoneMinder/lib/ZoneMinder/Filter.pm

@@ -322,14 +322,14 @@ sub Sql {
           if ( $term->{op} ) {
             # Handle special tag values before generic operators to avoid
             # LEFT JOIN NULL comparison issues with EXISTS/NOT EXISTS
-            if ( $term->{attr} eq 'Tags' and $term->{val} eq '0' ) {
+            if ( $term->{attr} eq 'Tags' and defined($term->{val}) and $term->{val} eq '0' ) {
               # "No Tag": = means no tags (NOT EXISTS), != means has tags (EXISTS)
               if ($term->{op} eq '!=' or $term->{op} eq 'IS NOT') {
                 $self->{Sql} .= 'EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
               } else {
                 $self->{Sql} .= 'NOT EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
               }
-            } elsif ( $term->{attr} eq 'Tags' and $term->{val} eq '-1' ) {
+            } elsif ( $term->{attr} eq 'Tags' and defined($term->{val}) and $term->{val} eq '-1' ) {
               # "Any Tag": = means has tags (EXISTS), != means no tags (NOT EXISTS)
               if ($term->{op} eq '!=' or $term->{op} eq 'IS NOT') {
                 $self->{Sql} .= 'NOT EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';

web/includes/FilterTerm.php

@@ -345,14 +345,14 @@ public function sql() {
       $sql .= '('.implode(' OR ', $subterms).')';
     } elseif (($this->attr === 'Tags') && ($values[0] === "'0'")) {
       // "No Tag": = means no tags (NOT EXISTS), != means has tags (EXISTS)
-      if ($this->op === '!=') {
+      if ($this->op === '!=' || $this->op === 'IS NOT') {
         $sql .= 'EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
       } else {
         $sql .= 'NOT EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
       }
     } elseif (($this->attr === 'Tags') && ($values[0] === "'-1'")) {
       // "Any Tag": = means has tags (EXISTS), != means no tags (NOT EXISTS)
-      if ($this->op === '!=') {
+      if ($this->op === '!=' || $this->op === 'IS NOT') {
         $sql .= 'NOT EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
       } else {
         $sql .= 'EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';