Check callable isn't NULL in _PyObject_CallMethodFormat

Author: johnslavik

Objects/call.c

@@ -729,6 +729,9 @@ _Py_COMP_DIAG_POP
 PyObject * _PyObject_CallMethodFormat(PyThreadState *tstate, PyObject *callable,
                                       const char *format, ...)
 {
+    if (callable == NULL) {
+        return NULL;
+    }
     va_list va;
     va_start(va, format);
     PyObject *retval = callmethod(tstate, callable, format, va);