placement: Stop detecting screen objects using `type(o.geometry)`.

All object type will now use tables instead of function, so this
check will break.

lib/awful/placement.lua

@@ -392,10 +392,12 @@ local function geometry_common(obj, args, new_geo, ignore_border_width)
             and obj.coords(new_geo) or obj.coords()
         return {x=coords.x, y=coords.y, width=0, height=0}
     elseif obj.geometry then
-        local geo = obj.geometry
+        if obj.get_bounding_geometry then
+            -- It is a screen, it doesn't support setting new sizes.
+            return obj:get_bounding_geometry(args)
+        end
 
         -- It is either a drawable or something that implement its API
-        if type(geo) == "function" then
         local dgeo = area_common(
             obj, fix_new_geometry(new_geo, args), ignore_border_width, args
         )
@@ -413,10 +415,6 @@ local function geometry_common(obj, args, new_geo, ignore_border_width)
         end
 
         return dgeo
-        end
-
-        -- It is a screen, it doesn't support setting new sizes.
-        return obj:get_bounding_geometry(args)
     else
         assert(false, "Invalid object")
     end
@@ -1462,7 +1460,7 @@ function placement.next_to(d, args)
     args = add_context(args, "next_to")
     d    = d or capi.client.focus
 
-    local osize = type(d.geometry) == "function"  and d:geometry() or nil
+    local osize = type(d.geometry) == "function"  and d:geometry() or d.geometry
     local original_pos, original_anchors = args.preferred_positions, args.preferred_anchors
 
     if type(original_pos) == "string" then