[pygobject] object: try to avoid calling PyObject_ClearWeakRefs()

[Christoph Reiter <creiter src gnome org>]

commit be895cafdb7197c92f428a40b4599f9af38cde28
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Mar 25 16:12:45 2018 +0200

    object: try to avoid calling PyObject_ClearWeakRefs()
    
    We only need to call PyObject_ClearWeakRefs if the weakref list is set.
    And since PyPy doesn't like PyObject_ClearWeakRefs this makes it work
    in the common case.

 gi/pygobject-object.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/gi/pygobject-object.c b/gi/pygobject-object.c
index 3c5e7af0..0bfeacc2 100644
--- a/gi/pygobject-object.c
+++ b/gi/pygobject-object.c
@@ -1084,7 +1084,9 @@ pygobject_dealloc(PyGObject *self)
      * object. */
     PyObject_GC_UnTrack((PyObject *)self);
 
-    PyObject_ClearWeakRefs((PyObject *)self);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
+
       /* this forces inst_data->type to be updated, which could prove
        * important if a new wrapper has to be created and it is of a
        * unregistered type */