tag_view: Update screen workarea

This partially fixes test-struts.lua. The test now fails at some later
part.

Fixes: https://github.com/awesomeWM/awesome/issues/1335
Signed-off-by: Uli Schlachter <psychon@znc.in>

objects/tag.c

@@ -178,6 +178,7 @@
  */
 
 #include "tag.h"
+#include "screen.h"
 #include "banning.h"
 #include "client.h"
 #include "ewmh.h"
@@ -277,6 +278,8 @@ tag_view(lua_State *L, int udx, bool view)
     {
         tag->selected = view;
         banning_need_update();
+        foreach(screen, globalconf.screens)
+            screen_update_workarea(*screen);
 
         luaA_object_emit_signal(L, udx, "property::selected", 0);
     }