fix(bar): avoid use-after-free segfault on exit

Members are destroyed in reverse declaration order, so modules_all_ (and
the modules it owns) are gone before the GtkWindow. Tearing down a mapped
window emits `unmap`, whose handler runs toggleSuspend() over the already
freed modules. Disconnect the map/unmap handlers in ~Bar first.

Fixes #5182

include/bar.hpp

@@ -131,6 +131,10 @@ class Bar : public sigc::trackable {
 
   waybar::util::KillSignalAction onSigusr1 = util::SIGNALACTION_DEFAULT_SIGUSR1;
   waybar::util::KillSignalAction onSigusr2 = util::SIGNALACTION_DEFAULT_SIGUSR2;
+
+  /* Disconnected in ~Bar before the modules are destroyed (#5182). */
+  sigc::connection map_conn_;
+  sigc::connection unmap_conn_;
 };
 
 }  // namespace waybar