Unbreak Forge logic.

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -94,14 +94,15 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
                 serverConn.getPlayer().sendLegacyForgeHandshakeResetPacket();
             }
 
-            // Always forward these messages during login
+            // Always forward these messages during login. Don't pass it onto the handleGeneric below.
             return false;
         }
 
         ChannelIdentifier id = server.getChannelRegistrar().getFromId(packet.getChannel());
         if (id == null) {
-            serverConn.getPlayer().getConnection().write(packet);
-        } else {
+            return false;
+        }
+
         PluginMessageEvent event = new PluginMessageEvent(serverConn, serverConn.getPlayer(), id, packet.getData());
         server.getEventManager().fire(event)
                 .thenAcceptAsync(pme -> {
@@ -109,7 +110,6 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
                         serverConn.getPlayer().getConnection().write(packet);
                     }
                 }, serverConn.getConnection().eventLoop());
-        }
         return true;
     }
 
@@ -134,11 +134,9 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
             return;
         }
 
-        if (serverConn.hasCompletedJoin()) {
         // Just forward the packet on. We don't have anything to handle at this time.
         serverConn.getPlayer().getConnection().write(packet);
     }
-    }
 
     @Override
     public void handleUnknown(ByteBuf buf) {
@@ -149,10 +147,8 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
             return;
         }
 
-        if (serverConn.hasCompletedJoin()) {
         serverConn.getPlayer().getConnection().write(buf.retain());
     }
-    }
 
     @Override
     public void exception(Throwable throwable) {