Fixed some multithreading bugs and crashes

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

@@ -11,6 +11,7 @@ import com.badlogic.gdx.utils.ObjectMap;
 import com.badlogic.gdx.utils.reflect.ClassReflection;
 import io.anuke.mindustry.io.Platform;
 import io.anuke.mindustry.net.Packet.ImportantPacket;
+import io.anuke.mindustry.net.Packet.UnimportantPacket;
 import io.anuke.mindustry.net.Packets.KickReason;
 import io.anuke.mindustry.net.Streamable.StreamBegin;
 import io.anuke.mindustry.net.Streamable.StreamBuilder;
@@ -189,7 +190,7 @@ public class Net{
 			if(clientLoaded || object instanceof ImportantPacket){
 				if(clientListeners.get(object.getClass()) != null) clientListeners.get(object.getClass()).accept(object);
 				if(listeners.get(object.getClass()) != null) listeners.get(object.getClass()).accept(object);
-			}else{
+			}else if(!(object instanceof UnimportantPacket)){
 				packetQueue.add(object);
 				Log.info("Queuing packet {0}.", ClassReflection.getSimpleName(object.getClass()));
 			}

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

@@ -7,4 +7,5 @@ public interface Packet {
     void write(ByteBuffer buffer);
 
     interface ImportantPacket{}
+    interface UnimportantPacket{}
 }

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

@@ -6,6 +6,7 @@ import io.anuke.mindustry.entities.Player;
 import io.anuke.mindustry.entities.SyncEntity;
 import io.anuke.mindustry.io.Version;
 import io.anuke.mindustry.net.Packet.ImportantPacket;
+import io.anuke.mindustry.net.Packet.UnimportantPacket;
 import io.anuke.mindustry.resource.Item;
 import io.anuke.ucore.entities.Entities;
 import io.anuke.ucore.entities.EntityGroup;
@@ -502,7 +503,7 @@ public class Packets {
         public void read(ByteBuffer buffer) { }
     }
 
-    public static class ItemTransferPacket implements Packet{
+    public static class ItemTransferPacket implements Packet, UnimportantPacket{
         public int position;
         public byte rotation;
         public byte itemid;