Fixed crash on load

core/src/io/anuke/mindustry/ClientLauncher.java

@@ -73,12 +73,6 @@ public class ClientLauncher extends ApplicationCore{
         });
     }
 
-    private void post(){
-        for(ApplicationListener listener : modules){
-            listener.init();
-        }
-    }
-
     @Override
     public void add(ApplicationListener module){
         super.add(module);

core/src/io/anuke/mindustry/core/ContentLoader.java

@@ -163,7 +163,7 @@ public class ContentLoader{
                 return null;
             }
             if(temporaryMapper[type.ordinal()].length <= id || temporaryMapper[type.ordinal()][id] == null){
-                return getByID(type, 0); //default value is always ID 0
+                return (T)contentMap[type.ordinal()].get(0); //default value is always ID 0
             }
             return (T)temporaryMapper[type.ordinal()][id];
         }

core/src/io/anuke/mindustry/maps/Maps.java

@@ -2,6 +2,7 @@ package io.anuke.mindustry.maps;
 
 import io.anuke.arc.*;
 import io.anuke.arc.assets.*;
+import io.anuke.arc.assets.loaders.*;
 import io.anuke.arc.collection.*;
 import io.anuke.arc.collection.IntSet.*;
 import io.anuke.arc.files.*;
@@ -308,6 +309,7 @@ public class Maps{
     }
 
     public void loadPreviews(){
+        Array<Map> createNew = new Array<>();
 
         for(Map map : maps){
             //try to load preview
@@ -315,7 +317,7 @@ public class Maps{
                 //this may fail, but calls createNewPreview
                 Core.assets.load(new AssetDescriptor<>(map.previewFile().path() + "." + mapExtension, Texture.class, new MapPreviewParameter(map))).loaded = t -> map.texture = (Texture)t;
             }else{
-                Core.app.post(() -> createNewPreview(map));
+                createNew.add(map);
             }
 
             try{
@@ -323,6 +325,8 @@ public class Maps{
             }catch(Exception ignored){
             }
         }
+
+        ((CustomLoader)Core.assets.getLoader(Content.class)).loaded = () -> Core.app.post(() -> createNew.each(this::createNewPreview));
     }
 
     public void createNewPreview(Map map){