Ignore empty messages (not just null) for join and quit

src/main/java/net/minecraft/server/NetServerHandler.java

@@ -648,7 +648,7 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
         a.info(this.player.name + " lost connection: " + s);
         // CraftBukkit start - we need to handle custom quit messages
         String quitMessage = this.minecraftServer.serverConfigurationManager.disconnect(this.player);
-        if (quitMessage != null) {
+        if ((quitMessage != null) && (quitMessage.length() > 0)) {
             this.minecraftServer.serverConfigurationManager.sendAll(new Packet3Chat(quitMessage));
         }
         // CraftBukkit end

src/main/java/net/minecraft/server/ServerConfigurationManager.java

@@ -130,7 +130,7 @@ public class ServerConfigurationManager {
 
         String joinMessage = playerJoinEvent.getJoinMessage();
 
-        if (joinMessage != null) {
+        if ((joinMessage != null) && (joinMessage.length() > 0)) {
             this.server.serverConfigurationManager.sendAll(new Packet3Chat(joinMessage));
         }
         // CraftBukkit end