fix "do not prematurely disconnect players on stop" (#13625)

Author: Gerrygames

paper-server/patches/sources/net/minecraft/network/PacketProcessor.java.patch

@@ -1,6 +1,6 @@
 --- a/net/minecraft/network/PacketProcessor.java
 +++ b/net/minecraft/network/PacketProcessor.java
-@@ -19,6 +_,22 @@
+@@ -19,15 +_,42 @@
          this.runningThread = runningThread;
      }
 
@@ -23,9 +23,11 @@
      public boolean isSameThread() {
          return Thread.currentThread() == this.runningThread;
      }
-@@ -27,7 +_,18 @@
+ 
+     public <T extends PacketListener> void scheduleIfPossible(T listener, Packet<T> packet) {
          if (this.closed) {
-             throw new RejectedExecutionException("Server already shutting down");
+-            throw new RejectedExecutionException("Server already shutting down");
++            throw new io.papermc.paper.util.ServerStopRejectedExecutionException("Server already shutting down"); // Paper - do not prematurely disconnect players on stop
          } else {
 -            this.packetsToBeHandled.add(new PacketProcessor.ListenerAndPacket<>(listener, packet));
 +            // Paper start - improve tick loop