[gnome-photos] operation-insta-filter: Assert that it's attached before creating graph

[Debarshi Ray <debarshir src gnome org>]

commit 132866ea5e67eac737613fc3abc1c394d1944b5c
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Dec 11 00:28:39 2017 +0100

    operation-insta-filter: Assert that it's attached before creating graph

 src/photos-operation-insta-filter.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-operation-insta-filter.c b/src/photos-operation-insta-filter.c
index cddb934..657e144 100644
--- a/src/photos-operation-insta-filter.c
+++ b/src/photos-operation-insta-filter.c
@@ -56,6 +56,10 @@ photos_operation_insta_filter_setup (PhotosOperationInstaFilter *self)
   GeglOperation *operation = GEGL_OPERATION (self);
   GeglNode *node;
 
+  g_return_if_fail (GEGL_IS_NODE (operation->node));
+  g_return_if_fail (GEGL_IS_NODE (self->input));
+  g_return_if_fail (GEGL_IS_NODE (self->output));
+
   g_list_free_full (self->nodes, g_object_unref);
   self->nodes = NULL;