Add default block in IdleStateHandler (#11341)

Motivation:

We should have a default case in every switch block.

Modification:

Add default block in IdleStateHandler

Result:

Cleanup

Signed-off-by: xingrufei <xingrufei@sogou-inc.com>

handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java

@@ -312,6 +312,8 @@ public class IdleStateHandler extends ChannelDuplexHandler {
         case 1:
         case 2:
             return;
+        default:
+             break;
         }
 
         state = 1;