Add NMS check information on startup

TradeSystem-Spigot/src/main/java/de/codingair/tradesystem/spigot/TradeSystem.java

@@ -3,6 +3,7 @@
 import de.codingair.codingapi.API;
 import de.codingair.codingapi.files.ConfigFile;
 import de.codingair.codingapi.files.FileManager;
+import de.codingair.codingapi.nms.NmsCheck;
 import de.codingair.codingapi.player.chat.ChatButtonManager;
 import de.codingair.codingapi.server.specification.Version;
 import de.codingair.codingapi.utils.Value;
@@ -40,6 +41,7 @@
 import org.jetbrains.annotations.NotNull;
 
 import java.io.FileNotFoundException;
+import java.util.logging.Level;
 
 public class TradeSystem extends JavaPlugin implements Proxy {
     private static TradeSystem instance;
@@ -62,6 +64,7 @@ public class TradeSystem extends JavaPlugin implements Proxy {
     private TradeCMD tradeCMD;
 
     private boolean firstSetup;
+    private boolean workingNms = false;
     private YamlConfiguration oldConfig;
 
     public static void log(String message) {
@@ -95,6 +98,8 @@ public static InvitationManager invitations() {
     @Override
     public void onEnable() {
         instance = this;
+        checkNms();
+
         API.getInstance().onEnable(this);
 
         printConsoleInfo(() -> {
@@ -130,6 +135,12 @@ public void onEnable() {
 
     @Override
     public void onDisable() {
+        if (!workingNms) {
+            getLogger().log(Level.SEVERE, "This Minecraft version does not seem to be supported yet. Please contact the author with the given error above.");
+            getLogger().log(Level.SEVERE, "Here's an invitation to the discord for support: https://discord.gg/DxKMcGjQbp");
+            return;
+        } else workingNms = false;
+
         API.getInstance().onDisable(this);
         Bukkit.getScheduler().cancelTasks(this);
 
@@ -179,6 +190,11 @@ private void printConsoleInfo(Runnable runnable) {
         log(" ");
     }
 
+    private void checkNms() {
+        NmsCheck.test(new Class[0]);
+        workingNms = true;
+    }
+
     private void loadManagers() {
         this.tradeHandler.load();
         this.layoutManager.load();