(Columns) adapt to phps 8.2

Adapt columns class to php 8.2

include/management/columns/class_Column.inc

@@ -50,7 +50,7 @@ class Column
     if (isset($data['attributes'])) {
       $attributes = $data['attributes'];
       if (!is_array($attributes)) {
-        $attributes = array_map('trim', explode(',', $attributes));
+        $attributes = array_map('trim', explode(',', (string) $attributes));
       }
     }
     if (isset($data['label'])) {
@@ -216,9 +216,9 @@ class Column
         if ($b == '') {
           $b = '31.12.0000';
         }
-        list($d, $m, $y) = explode('.', $a);
+        list($d, $m, $y) = explode('.', (string) $a);
         $a = (int)sprintf('%04d%02d%02d', $y, $m, $d);
-        list($d, $m, $y) = explode('.', $b);
+        list($d, $m, $y) = explode('.', (string) $b);
         $b = (int)sprintf('%04d%02d%02d', $y, $m, $d);
         return $b - $a;