diff -r 18892c0a9adc -r b70e2a77dea0 ui/gtk/toolkit.c
--- a/ui/gtk/toolkit.c	Sat Dec 05 11:54:58 2020 +0100
+++ b/ui/gtk/toolkit.c	Sat Dec 05 17:50:22 2020 +0100
@@ -182,6 +182,7 @@
     if(!result) {
         g_idle_add(ui_job_finished, job);
     }
+    return NULL;
 }
 
 void ui_job(UiObject *obj, ui_threadfunc tf, void *td, ui_callback f, void *fd) {