--- a/ui/gtk/toolbar.c	Sat Dec 05 11:54:58 2020 +0100
+++ b/ui/gtk/toolbar.c	Sat Dec 05 17:50:22 2020 +0100
@@ -168,6 +168,8 @@
     UiVar *var = malloc(sizeof(UiVar));
     var->value = list;
     var->type = UI_VAR_SPECIAL;
+    var->from = NULL;
+    var->from_ctx = NULL;
     cb->var = var;
     cb->getvalue = getvalue;
     cb->callback = f;