[gegl] operation: Be more strict about what is acceptable

[Debarshi Ray <debarshir src gnome org>]

commit ed72856ade4ec0be5fba76db09698b8992fd2dfd
Author: Debarshi Ray <debarshir gnome org>
Date:   Tue Dec 19 07:43:19 2017 +0100

    operation: Be more strict about what is acceptable

 gegl/operation/gegl-operation.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gegl/operation/gegl-operation.c b/gegl/operation/gegl-operation.c
index 2ce406f..cb058b5 100644
--- a/gegl/operation/gegl-operation.c
+++ b/gegl/operation/gegl-operation.c
@@ -181,6 +181,9 @@ gegl_operation_get_bounding_box (GeglOperation *self)
   GeglOperationClass *klass = GEGL_OPERATION_GET_CLASS (self);
   GeglRectangle       rect  = { 0, 0, 0, 0 };
 
+  g_return_val_if_fail (GEGL_IS_OPERATION (self), rect);
+  g_return_val_if_fail (GEGL_IS_NODE (self->node), rect);
+
   if (self->node->passthrough)
   {
     GeglRectangle  result = { 0, 0, 0, 0 };