Fix exception on 1.20.6 with Spigot (EssentialsX#5820)

How could I forget to update the md_5 magic letter

Fixes EssentialsX#5818

Author: JRoy

providers/NMSReflectionProvider/src/main/java/net/ess3/nms/refl/ReflUtil.java

@@ -22,6 +22,7 @@ public final class ReflUtil {
     public static final NMSVersion V1_18_R1 = NMSVersion.fromString("v1_18_R1");
     public static final NMSVersion V1_19_R1 = NMSVersion.fromString("v1_19_R1");
     public static final NMSVersion V1_19_R2 = NMSVersion.fromString("v1_19_R2");
+    public static final NMSVersion V1_20_R4 = NMSVersion.fromString("v1_20_R4");
     private static final Map<String, Class<?>> classCache = new HashMap<>();
     private static final Table<Class<?>, String, Method> methodCache = HashBasedTable.create();
     private static final Table<Class<?>, MethodParams, Method> methodParamCache = HashBasedTable.create();

providers/NMSReflectionProvider/src/main/java/net/ess3/nms/refl/providers/ReflServerStateProvider.java

@@ -16,7 +16,9 @@ public ReflServerStateProvider() {
         MethodHandle isRunning = null;
 
         final String MDFIVEMAGICLETTER;
-        if (ReflUtil.getNmsVersionObject().isHigherThanOrEqualTo(ReflUtil.V1_19_R2)) {
+        if (ReflUtil.getNmsVersionObject().isHigherThanOrEqualTo(ReflUtil.V1_20_R4)) {
+            MDFIVEMAGICLETTER = "x";
+        } else if (ReflUtil.getNmsVersionObject().isHigherThanOrEqualTo(ReflUtil.V1_19_R2)) {
             MDFIVEMAGICLETTER = "v";
         } else if (ReflUtil.getNmsVersionObject().isHigherThanOrEqualTo(ReflUtil.V1_19_R1)) {
             MDFIVEMAGICLETTER = "u";