diff -r 29d98cff4f56 -r 853685152c1d ui/gtk/button.c
--- a/ui/gtk/button.c	Sat Nov 11 12:22:16 2017 +0100
+++ b/ui/gtk/button.c	Sun Nov 12 12:03:50 2017 +0100
@@ -122,6 +122,7 @@
         UiVarEventData *event = malloc(sizeof(UiVarEventData));
         event->obj = obj;
         event->var = var;
+        event->observers = NULL;
 
         g_signal_connect(
                 button,
@@ -179,6 +180,7 @@
         UiVarEventData *event = malloc(sizeof(UiVarEventData));
         event->obj = obj;
         event->var = var;
+        event->observers = NULL;
         
         g_signal_connect(
                 rbutton,