Fix problem that a missing GET parameter 'recordHashMd5' always trigger 'record modified'

extension/qfq/qfq/form/Dirty.php

@@ -242,6 +242,10 @@ class Dirty {
      */
     private function isRecordModified($tableName, $recordId, $recordHashMd5, &$rcMd5) {
 
+        if($recordHashMd5 =='') {
+            return false; // If there is no recordHashMd5, the check is not possible. Always return 'not modified' (=ok)
+        }
+
         $record = $this->db->sql("SELECT * FROM $tableName WHERE id=?", ROW_EXPECT_1, [$recordId], "Record to lock not found.");
 
         $rcMd5 = OnArray::getMd5($record);