focus_order_remove is called in a few places. move the check for unsetting focus_client into client_unmanage.

openbox/client.c

@@ -535,6 +535,9 @@ void client_unmanage(ObClient *self)
 
     /* update the focus lists */
     focus_order_remove(self);
+    /* don't leave an invalid focus_client */
+    if (self == focus_client)
+        focus_client = NULL;
 
     client_list = g_list_remove(client_list, self);
     stacking_remove(self);

openbox/focus.c

@@ -273,6 +273,8 @@ void focus_fallback(gboolean allow_refocus)
     */
     focus_nothing();
 
+    focus_client = NULL;
+
     if ((new = focus_fallback_target(allow_refocus, old)))
         client_focus(new);
 }
@@ -285,8 +287,6 @@ void focus_nothing()
         screen_install_colormap(NULL, TRUE);
     }
 
-    focus_client = NULL;
-
     /* when nothing will be focused, send focus to the backup target */
     XSetInputFocus(ob_display, screen_support_win, RevertToPointerRoot,
                    event_curtime);
@@ -763,8 +763,6 @@ void focus_order_add_new(ObClient *c)
 void focus_order_remove(ObClient *c)
 {
     focus_order = g_list_remove(focus_order, c);
-    if (c == focus_client)
-        focus_client = NULL;
 }
 
 void focus_order_to_top(ObClient *c)