it is done

core/src/mindustry/maps/MapPreviewLoader.java

@@ -0,0 +1,57 @@
+package mindustry.maps;
+
+import arc.assets.*;
+import arc.assets.loaders.*;
+import arc.assets.loaders.resolvers.*;
+import arc.struct.*;
+import arc.files.*;
+import arc.graphics.*;
+import arc.util.*;
+import mindustry.*;
+import mindustry.ctype.Content;
+
+public class MapPreviewLoader extends TextureLoader{
+
+    public MapPreviewLoader(){
+        super(new AbsoluteFileHandleResolver());
+    }
+
+    @Override
+    public void loadAsync(AssetManager manager, String fileName, Fi file, TextureParameter parameter){
+        try{
+            super.loadAsync(manager, fileName, file.sibling(file.nameWithoutExtension()), parameter);
+        }catch(Exception e){
+            Log.err(e);
+            MapPreviewParameter param = (MapPreviewParameter)parameter;
+            Vars.maps.queueNewPreview(param.map);
+        }
+    }
+
+    @Override
+    public Texture loadSync(AssetManager manager, String fileName, Fi file, TextureParameter parameter){
+        try{
+            return super.loadSync(manager, fileName, file, parameter);
+        }catch(Throwable e){
+            Log.err(e);
+            try{
+                return new Texture(file);
+            }catch(Throwable e2){
+                Log.err(e2);
+                return new Texture("sprites/error.png");
+            }
+        }
+    }
+
+    @Override
+    public Array<AssetDescriptor> getDependencies(String fileName, Fi file, TextureParameter parameter){
+        return Array.with(new AssetDescriptor<>("contentcreate", Content.class));
+    }
+
+    public static class MapPreviewParameter extends TextureParameter{
+        public Map map;
+
+        public MapPreviewParameter(Map map){
+            this.map = map;
+        }
+    }
+}