Fix plugin startup without ProtocolLib installed

Referencing `ProtocolLibrary` in FastLoginBukkit (even in an unreachable
code block) causes Bukkit servers to throw a NoClassDefFoundError on
startup.
Fix based on commit 0082cc6

Author: Smart123s

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/FastLoginBukkit.java

@@ -25,7 +25,6 @@
  */
 package com.github.games647.fastlogin.bukkit;
 
-import com.comphenix.protocol.ProtocolLibrary;
 import com.github.games647.fastlogin.bukkit.command.CrackedCommand;
 import com.github.games647.fastlogin.bukkit.command.PremiumCommand;
 import com.github.games647.fastlogin.bukkit.listener.ConnectionListener;
@@ -121,7 +120,7 @@ public void onEnable() {
 
                 if (isPluginInstalled("floodgate")) {
                     if (getConfig().getBoolean("floodgatePrefixWorkaround")){
-                        ProtocolLibrary.getProtocolManager().addPacketListener(new ManualNameChange(this, floodgateService));
+                        ManualNameChange.register(this, floodgateService);
                         logger.info("Floodgate prefix injection workaround has been enabled.");
                         logger.info("If you have problems joining the server, try disabling it in the configuration.");
                     } else {

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/listener/protocollib/ManualNameChange.java

@@ -36,6 +36,8 @@
 
 import static com.comphenix.protocol.PacketType.Login.Client.START;
 
+import com.comphenix.protocol.ProtocolLibrary;
+
 /**
  * Manually inject Floodgate player name prefixes.
  * <br>
@@ -57,6 +59,14 @@ public ManualNameChange(FastLoginBukkit plugin, FloodgateService floodgate) {
         this.floodgate = floodgate;
     }
 
+    public static void register(FastLoginBukkit plugin, FloodgateService floodgate) {
+        // they will be created with a static builder, because otherwise it will throw a NoClassDefFoundError
+        ProtocolLibrary.getProtocolManager()
+                .getAsynchronousManager()
+                .registerAsyncHandler(new ManualNameChange(plugin, floodgate))
+                .start();
+    }
+
     @Override
     public void onPacketReceiving(PacketEvent packetEvent) {
         PacketContainer packet = packetEvent.getPacket();