Revert "bpo-44562: Remove invalid PyObject_GC_Del from error path of types.GenericAlias … (GH-27016) (GH-27018)" (GH-27022)

This reverts commit 4684a34.

Author: pablogsal

Misc/NEWS.d/next/Core and Builtins/2021-07-04-23-38-51.bpo-44562.QdeRQo.rst

@@ -602,7 +602,7 @@ ga_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         return NULL;
     }
     if (!setup_ga(self, origin, arguments)) {
-        Py_DECREF(self);
+        type->tp_free((PyObject *)self);
         return NULL;
     }
     return (PyObject *)self;
@@ -644,10 +644,10 @@ Py_GenericAlias(PyObject *origin, PyObject *args)
     if (alias == NULL) {
         return NULL;
     }
-    _PyObject_GC_TRACK(alias);
     if (!setup_ga(alias, origin, args)) {
-        Py_DECREF(alias);
+        PyObject_GC_Del((PyObject *)alias);
         return NULL;
     }
+    _PyObject_GC_TRACK(alias);
     return (PyObject *)alias;
 }