awesome FS#503 unregister systray .patch

diff --git a/objects/wibox.c b/objects/wibox.c
index c33f77f..fd69fb4 100644
--- a/objects/wibox.c
+++ b/objects/wibox.c
@@ -431,6 +431,10 @@ wibox_systray_kickout(int phys_screen)
 static void
 wibox_systray_refresh(wibox_t *wibox)
 {
+    bool systray_found = false;
+    int phys_screen = wibox->ctx.phys_screen;
+    screen_t screen = globalconf.screens.tab[phys_screen];
+
     if(!wibox->screen)
         return;
 
@@ -443,9 +447,8 @@ wibox_systray_refresh(wibox_t *wibox)
             uint32_t config_win_vals[4];
             uint32_t config_win_vals_off[2] = { -512, -512 };
             xembed_window_t *em;
-            int phys_screen = wibox->ctx.phys_screen;
-            screen_t screen = globalconf.screens.tab[phys_screen];
 
+            systray_found = true;
             if(!screen.systray.registered)
                 systray_register(phys_screen);
 
@@ -590,6 +593,9 @@ wibox_systray_refresh(wibox_t *wibox)
             break;
         }
     }
+
+    if(!systray_found && screen.systray.registered)
+        systray_cleanup(phys_screen);
 }
 
 /** Get a wibox by its window.