Fix leak of backed_enum_table with preloading

Author: iluuu1994

Zend/zend_opcode.c

@@ -275,6 +275,12 @@ ZEND_API void zend_cleanup_mutable_class_data(zend_class_entry *ce)
 			mutable_data->default_properties_table = NULL;
 		}
 
+		// backed_enum_table is allocated as part of the request. Thus it's implicitly mutable data.
+		if (ce->backed_enum_table) {
+			zend_hash_release(ce->backed_enum_table);
+			ce->backed_enum_table = NULL;
+		}
+
 		ZEND_MAP_PTR_SET_IMM(ce->mutable_data, NULL);
 	}
 }