Add more missing PyErr_NoMemory() after failled memory allocs
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 6a358da..14318f6 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6661,7 +6661,7 @@
 	if (pnew->str == NULL) {
 		_Py_ForgetReference((PyObject *)pnew);
 		PyObject_Del(pnew);
-		return NULL;
+		return PyErr_NoMemory();
 	}
 	Py_UNICODE_COPY(pnew->str, tmp->str, n+1);
 	pnew->length = n;