Remove sprite batch stuff and make sure nil values are removed from the entities list

src/play_clj/core.clj

@@ -29,6 +29,7 @@
                   (some->> (func @screen @entities)
                            list
                            flatten
+                           (remove nil?)
                            (reset! entities)))]
     (proxy [Screen] []
       (show []

src/play_clj/core_2d.clj

@@ -2,15 +2,6 @@
 
 ; drawing
 
-(defmulti sprite-batch #(-> % :renderer class) :default nil)
-
-(defmethod sprite-batch nil [screen]
-  (SpriteBatch.))
-
-(defmethod sprite-batch BatchTiledMapRenderer [{:keys [renderer]}]
-  (assert renderer)
-  (.getSpriteBatch renderer))
-
 (defn draw! [{:keys [renderer]} entities]
   (assert renderer)
   (let [batch (.getSpriteBatch renderer)]