remove the urgency indicator when a window is closed

src/tree.c

@@ -200,6 +200,13 @@ bool tree_close(Con *con, kill_window_t kill_window, bool dont_kill_parent, bool
         was_mapped = _is_con_mapped(con);
     }
 
+    /* remove the urgency hint of the workspace (if set) */
+    if (con->urgent) {
+        con->urgent = false;
+        con_update_parents_urgency(con);
+        workspace_update_urgent_flag(con_get_workspace(con));
+    }
+
     /* Get the container which is next focused */
     Con *next = con_next_focused(con);
     DLOG("next = %p, focused = %p\n", next, focused);