Check PyLong_AsVoidPtr result (#9548)

src/_imagingtk.c

@@ -33,8 +33,10 @@ _tkinit(PyObject *self, PyObject *args) {
     }
 
     interp = (Tcl_Interp *)PyLong_AsVoidPtr(arg);
+    if (interp == NULL && PyErr_Occurred()) {
+        return NULL;
+    }
 
-    /* This will bomb if interp is invalid... */
     TkImaging_Init(interp);
 
     Py_RETURN_NONE;