Fix issue when exiting server when plugin manager hasn't loaded

src/main/java/emu/grasscutter/Grasscutter.java

 package emu.grasscutter;
 
-import java.io.*;
-import java.util.Calendar;
-
+import ch.qos.logback.classic.Logger;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import emu.grasscutter.auth.AuthenticationSystem;
 import emu.grasscutter.auth.DefaultAuthentication;
 import emu.grasscutter.command.CommandMap;
 import emu.grasscutter.command.DefaultPermissionHandler;
 import emu.grasscutter.command.PermissionHandler;
 import emu.grasscutter.game.dungeons.challenge.DungeonChallenge;
+import emu.grasscutter.data.ResourceLoader;
+import emu.grasscutter.database.DatabaseManager;
 import emu.grasscutter.game.managers.energy.EnergyManager;
 import emu.grasscutter.game.managers.stamina.StaminaManager;
 import emu.grasscutter.plugin.PluginManager;
 import emu.grasscutter.plugin.api.ServerHook;
 import emu.grasscutter.scripts.ScriptLoader;
+import emu.grasscutter.server.game.GameServer;
 import emu.grasscutter.server.http.HttpServer;
 import emu.grasscutter.server.http.dispatch.DispatchHandler;
-import emu.grasscutter.server.http.handlers.*;
 import emu.grasscutter.server.http.dispatch.RegionHandler;
 import emu.grasscutter.server.http.documentation.DocumentationServerHandler;
+import emu.grasscutter.server.http.handlers.AnnouncementsHandler;
+import emu.grasscutter.server.http.handlers.GachaHandler;
+import emu.grasscutter.server.http.handlers.GenericHandler;
+import emu.grasscutter.server.http.handlers.LogHandler;
+import emu.grasscutter.tools.Tools;
 import emu.grasscutter.utils.ConfigContainer;
+import emu.grasscutter.utils.Crypto;
+import emu.grasscutter.utils.Language;
 import emu.grasscutter.utils.Utils;
 import org.jline.reader.EndOfFileException;
 import org.jline.reader.LineReader;
@@ -30,21 +39,13 @@ import org.jline.terminal.TerminalBuilder;
 import org.reflections.Reflections;
 import org.slf4j.LoggerFactory;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-
-import ch.qos.logback.classic.Logger;
-import emu.grasscutter.data.ResourceLoader;
-import emu.grasscutter.database.DatabaseManager;
-import emu.grasscutter.utils.Language;
-import emu.grasscutter.server.game.GameServer;
-import emu.grasscutter.tools.Tools;
-import emu.grasscutter.utils.Crypto;
-
 import javax.annotation.Nullable;
+import java.io.*;
+import java.util.Calendar;
 
+import static emu.grasscutter.Configuration.DATA;
+import static emu.grasscutter.Configuration.SERVER;
 import static emu.grasscutter.utils.Language.translate;
-import static emu.grasscutter.Configuration.*;
 
 public final class Grasscutter {
     private static final Logger log = (Logger) LoggerFactory.getLogger(Grasscutter.class);
@@ -90,19 +91,22 @@ public final class Grasscutter {
         for (String arg : args) {
             switch (arg.toLowerCase()) {
                 case "-handbook" -> {
-					Tools.createGmHandbook(); exitEarly = true;
+                    Tools.createGmHandbook();
+                    exitEarly = true;
                 }
                 case "-gachamap" -> {
-					Tools.createGachaMapping(DATA("gacha_mappings.js")); exitEarly = true;
+                    Tools.createGachaMapping(DATA("gacha_mappings.js"));
+                    exitEarly = true;
                 }
                 case "-version" -> {
-					System.out.println("Grasscutter version: " + BuildConfig.VERSION + "-" + BuildConfig.GIT_HASH); exitEarly = true;
+                    System.out.println("Grasscutter version: " + BuildConfig.VERSION + "-" + BuildConfig.GIT_HASH);
+                    exitEarly = true;
                 }
             }
         }
 
         // Exit early if argument sets it.
-		if(exitEarly) System.exit(0);
+        if (exitEarly) System.exit(0);
 
         // Initialize server.
         Grasscutter.getLogger().info(translate("messages.status.starting"));
@@ -113,8 +117,6 @@ public final class Grasscutter {
         Grasscutter.updateDayOfWeek();
         ResourceLoader.loadAll();
         ScriptLoader.init();
-		EnergyManager.initialize();
-		DungeonChallenge.initialize();
 
         // Initialize database.
         DatabaseManager.initialize();
@@ -142,9 +144,6 @@ public final class Grasscutter {
         httpServer.addRouter(GachaHandler.class);
         httpServer.addRouter(DocumentationServerHandler.class);
 
-		// TODO: find a better place?
-		StaminaManager.initialize();
-	
         // Start servers.
         var runMode = SERVER.runMode;
         if (runMode == ServerRunMode.HYBRID) {
@@ -176,6 +175,7 @@ public final class Grasscutter {
      */
     private static void onShutdown() {
         // Disable all plugins.
+        if(pluginManager != null)
             pluginManager.disablePlugins();
     }
 
@@ -215,10 +215,11 @@ public final class Grasscutter {
 
     /**
      * Saves the provided server configuration.
+     *
      * @param config The configuration to save, or null for a new one.
      */
     public static void saveConfig(@Nullable ConfigContainer config) {
-		if(config == null) config = new ConfigContainer();
+        if (config == null) config = new ConfigContainer();
 
         try (FileWriter file = new FileWriter(configFile)) {
             file.write(gson.toJson(config));
@@ -350,6 +351,7 @@ public final class Grasscutter {
 
     /**
      * Sets the authentication system for the server.
+     *
      * @param authenticationSystem The authentication system to use.
      */
     public static void setAuthenticationSystem(AuthenticationSystem authenticationSystem) {
@@ -358,6 +360,7 @@ public final class Grasscutter {
 
     /**
      * Sets the permission handler for the server.
+     *
      * @param permissionHandler The permission handler to use.
      */
     public static void setPermissionHandler(PermissionHandler permissionHandler) {