fix: Fix unrecognized functional index defined in MySQL

+ The issue leads to crashing dbal.
+ The column(s) is returned as null when the index is not recognised
+ The issue is fixed by skipping the creation of index if no columns are provided.

Author: junaidbinfarooq

src/Schema/AbstractSchemaManager.php

@@ -730,6 +730,10 @@ protected function _getPortableTableIndexesList(array $tableIndexes, string $tab
 
         $indexes = [];
         foreach ($result as $indexKey => $data) {
+            if (count($data['columns']) === 0) {
+                continue;
+            }
+
             $indexes[$indexKey] = new Index(
                 $data['name'],
                 $data['columns'],