Bugfixes

core/src/io/anuke/mindustry/net/NetworkIO.java

@@ -28,6 +28,7 @@ public class NetworkIO{
             stream.writeInt(player.id);
             player.write(stream);
 
+            SaveIO.getSaveWriter().writeContentHeader(stream);
             SaveIO.getSaveWriter().writeMap(stream);
         }catch(IOException e){
             throw new RuntimeException(e);
@@ -51,9 +52,12 @@ public class NetworkIO{
             player.resetID(id);
             player.add();
 
+            SaveIO.getSaveWriter().readContentHeader(stream);
             SaveIO.getSaveWriter().readMap(stream, world.context);
         }catch(IOException e){
             throw new RuntimeException(e);
+        }finally{
+            content.setTemporaryMapper(null);
         }
     }