Fix apps menu not popping up when menu icons disabled
When disabling menu icons, it causes the menu to stop loading and reload. Unfortunately, this changes the behavior of gtk_widget_show(), which usually waits for the menu's initial load to complete before returning. Since the no-icons reload is not the initial load, it doesn't wait.
This fix creates the menu by first setting the show-menu-icons property before setting the GarconMenu, the latter of which is what triggers the initial menu load. This way, gtk_widget_show() will always wait for the menu to be populated, regardless of the icons setting.
Addresses #220 (closed).
This fix will go on the 4.18 branch; I'm going to do something a little bit more involved for master/4.20 that is a bit "better", but I'd rather make a more minimal change to 4.18.