Fix login disconnect errors

SpigotCore_Main/src/com/comphenix/tinyprotocol/TinyProtocol.java

@@ -274,6 +274,9 @@ public class TinyProtocol {
 			// Inject our packet interceptor
 			if (interceptor == null) {
 				interceptor = new PacketInterceptor();
+				if(!channel.isActive())
+					return interceptor;
+
 				channel.pipeline().addBefore("packet_handler", handlerName, interceptor);
 				uninjectedChannels.remove(channel);
 			}