i3bar: Correctly handle removal of tray clients

i3bar/include/outputs.h

@@ -46,9 +46,8 @@ struct i3_output {
     xcb_pixmap_t   buffer;        /* An extra pixmap for double-buffering */
     xcb_gcontext_t bargc;         /* The graphical context of the bar */
 
-    int            traypx;        /* Amount of pixels reserved for tray icons */
-
     struct ws_head *workspaces;   /* The workspaces on this output */
+    struct tc_head *trayclients;  /* The tray clients on this output */
 
     SLIST_ENTRY(i3_output) slist; /* Pointer for the SLIST-Macro */
 };