pythongh-144851: Fix __lazy_import__ crash with user-defined filters (python#144852)

Author: johnslavik

Lib/test/test_lazy_import/__init__.py

@@ -391,6 +391,11 @@ def test_dunder_lazy_import(self):
         import test.test_lazy_import.data.dunder_lazy_import
         self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
 
+    def test_dunder_lazy_import_with_custom_filter(self):
+        sys.set_lazy_imports_filter(lambda importer, imported, fromlist: False)
+        import test.test_lazy_import.data.dunder_lazy_import
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
     def test_dunder_lazy_import_used(self):
         """Using __lazy_import__ result should trigger module load."""
         import test.test_lazy_import.data.dunder_lazy_import_used

Python/import.c

@@ -4512,6 +4512,10 @@ _PyImport_LazyImportModuleLevelObject(PyThreadState *tstate,
             assert(!PyErr_Occurred());
             modname = Py_NewRef(Py_None);
         }
+        if (fromlist == NULL) {
+            assert(!PyErr_Occurred());
+            fromlist = Py_NewRef(Py_None);
+        }
         PyObject *args[] = {modname, name, fromlist};
         PyObject *res = PyObject_Vectorcall(filter, args, 3, NULL);