place: Fix workspace check when collecting relevant windows

When looking for space to place a new window, other non-minimized
windows on the same workspace should be taken into account. However
the current check does not work correctly when the placed window is
located on all workspaces, so handle that case explicitly.

https://bugzilla.gnome.org/show_bug.cgi?id=743217

src/core/place.c

@@ -779,7 +779,8 @@ meta_window_place (MetaWindow        *window,
 
         if (w != window &&
             meta_window_showing_on_its_workspace (w) &&
-            meta_window_located_on_workspace (w, window->workspace))
+            (window->on_all_workspaces ||
+             meta_window_located_on_workspace (w, window->workspace)))
           windows = g_list_prepend (windows, w);
 
         tmp = tmp->next;