Fix reloading on Spigot

Fixes #3319

bootstrap/spigot/src/main/java/org/geysermc/geyser/platform/spigot/GeyserSpigotPlugin.java

@@ -196,6 +196,7 @@ public class GeyserSpigotPlugin extends JavaPlugin implements GeyserBootstrap {
 
         geyserConfig.loadFloodgate(this);
 
+        if (!INITIALIZED) {
             // Needs to be an anonymous inner class otherwise Bukkit complains about missing classes
             Bukkit.getPluginManager().registerEvents(new Listener() {
 
@@ -229,6 +230,12 @@ public class GeyserSpigotPlugin extends JavaPlugin implements GeyserBootstrap {
             }
         }
 
+        if (INITIALIZED) {
+            // Reload; continue with post startup
+            postStartup();
+        }
+    }
+
     private void postStartup() {
         GeyserImpl.start();