tests: Use rawget to avoid trigerring the tripwire.

The next commit will introduce extra checks that would otherwise
break this.

tests/examples/awful/template.lua

@@ -35,8 +35,8 @@ local function draw_mouse(x, y)
 end
 
 -- Print an outline for the screens
-if not screen.no_outline then
-    for _, s in ipairs(screen) do
+if not rawget(screen, "no_outline") then
+    for s in screen do
         cr:save()
         -- Draw the screen outline
         cr:set_source(color("#00000044"))

tests/examples/shims/screen.lua

@@ -78,7 +78,7 @@ end
 
 function screen._get_extents()
     local xmax, ymax
-    for _, v in ipairs(screen) do
+    for v in screen do
         if not xmax or v.geometry.x+v.geometry.width > xmax.geometry.x+xmax.geometry.width then
             xmax = v
         end