Update monarch.lua

Fixes #102

README_TRANSITIONS.md

@@ -114,7 +114,7 @@ end
 
 function on_message(self, message_id, message, sender)
 	if message_id == hash("my_resize_message") then
-		self.transition.window_resized(message.width, message.height)
+		transition.window_resized(message.width, message.height)
 	end
 end
 ```

monarch/monarch.lua

@@ -520,8 +520,12 @@ local function load(screen)
 		msg.post(screen.proxy, MSG_ENABLE)
 	elseif screen.factory then
 		screen.factory_ids = collectionfactory.create(screen.factory)
-		screen.transition_url = screen.factory_ids[screen.transition_id]
-		screen.focus_url = screen.factory_ids[screen.focus_id]
+		if screen.transition_id then
+			screen.transition_url = screen.factory_ids[screen.transition_id]
+		end
+		if screen.focus_id then
+			screen.focus_url = screen.factory_ids[screen.focus_id]
+		end
 	end
 	screen.loaded = true
 	screen.preloaded = false