[demo] fixes

src/main/haxework/provider/Provider.hx

@@ -65,8 +65,7 @@ abstract KeyType<T>(String) {
             instances.set(key, instance);
             return instance;
         } else {
-            return null;
-            //throw 'Factory for "${key}" not found';
+            throw 'Factory for "${key}" not found';
         }
     }