Fix: SearchPane option ordering could give a deprecated warning if nu…

…ll data is present

https://datatables.net/forums/discussion/76266

Editor/SearchPaneOptions.php

@@ -444,9 +444,20 @@ public function exec ( $field, $editor, $http, $fields, $leftJoinIn )
 		// Only sort if there was no SQL order field
 		if ( ! $this->_order ) {
 			usort( $out, function ( $a, $b ) {
-				return is_numeric($a['label']) && is_numeric($b['label']) ?
-					($a['label']*1) - ($b['label']*1) :
-					strcmp( $a['label'], $b['label'] );
+				$aLabel = $a['label'];
+				$bLabel = $b['label'];
+
+				if ($aLabel === null) {
+					$aLabel = '';
+				}
+
+				if ($bLabel === null) {
+					$bLabel = '';
+				}
+
+				return is_numeric($aLabel) && is_numeric($bLabel) ?
+					($aLabel*1) - ($bLabel*1) :
+					strcmp( $aLabel, $bLabel );
 			} );
 		}