gst_mini_object_replace() can take NULL mini-objects.
https://bugzilla.gnome.org/show_bug.cgi?id=730873
/**
* gst_mini_object_replace:
- * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
- * be replaced
- * @newdata: pointer to new mini-object
+ * @olddata: (inout) (transfer full) (nullable): pointer to a pointer to a
+ * mini-object to be replaced
+ * @newdata: (nullable): pointer to new mini-object
*
* Atomically modifies a pointer to point to a new mini-object.
* The reference count of @olddata is decreased and the reference count of