fix(Registry): make registry php 7.4 compatible

Deprecated: array_key_exists(): Using array_key_exists()
 on objects is deprecated. Use isset() or property_exists()
 instead

see tine20/tine20#7125

library/Zend/Registry.php

@@ -203,7 +203,6 @@ public function __construct($array = array(), $flags = parent::ARRAY_AS_PROPS)
      */
     public function offsetExists($index)
     {
-        return array_key_exists($index, $this);
+        return isset($this->{$index});
     }
-
 }