bpo-44531: Fix type_repr() if tp_name is NULL (GH-26948)

Allow to call type_repr() on a type which is not fully initialized
yet. This fix helps debugging crashes occurring early at Python
initialization.

Objects/typeobject.c

@@ -1065,6 +1065,12 @@ static PyGetSetDef type_getsets[] = {
 static PyObject *
 type_repr(PyTypeObject *type)
 {
+    if (type->tp_name == NULL) {
+        // type_repr() called before the type is fully initialized
+        // by PyType_Ready().
+        return PyUnicode_FromFormat("<class at %p>", type);
+    }
+
     PyObject *mod, *name, *rtn;
 
     mod = type_module(type, NULL);