[gtk/prop-list: 185/199] filter: Add a missing precondition

[Matthias Clasen <matthiasc src gnome org>]

commit 10312e5f0d68affec8c695e2f14ef77b1d644f11
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Dec 8 13:08:30 2019 -0500

    filter: Add a missing precondition

 gtk/gtkfilters.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gtk/gtkfilters.c b/gtk/gtkfilters.c
index 9a0157b466..01dc740248 100644
--- a/gtk/gtkfilters.c
+++ b/gtk/gtkfilters.c
@@ -255,6 +255,8 @@ gtk_any_filter_remove (GtkAnyFilter *self,
   GSequenceIter *iter;
   guint length;
 
+  g_return_if_fail (GTK_IS_ANY_FILTER (self));
+
   length = g_sequence_get_length (self->filters);
   if (position >= length)
     return;