Fix bug with titleview close button not working

The bug was actually due to a presence of a ghost tab scrolling button
in all the views.

We need to check if the node has multiple views, if not there are no tabs
and therefore no scrolling button areas so we return nothing from the
method Node:get_scroll_button_index().

Close #216

data/core/rootview.lua

@@ -272,6 +272,7 @@ end
 
 
 function Node:get_scroll_button_index(px, py)
+  if #self.views == 1 then return 0 end
   for i = 1, 2 do
     local x, y, w, h = self:get_scroll_button_rect(i)
     if px >= x and px < x + w and py >= y and py < y + h then