Add null check to namedGroups property

Author: SupremeMortal

bedrock/bedrock-common/src/main/java/com/nukkitx/protocol/bedrock/util/EncryptionUtils.java

@@ -43,7 +43,7 @@ public class EncryptionUtils {
         // DO NOT REMOVE THIS
         // Since Java 8u231, secp384r1 is deprecated and will throw an exception.
         String namedGroups = System.getProperty("jdk.tls.namedGroups");
-        System.setProperty("jdk.tls.namedGroups", namedGroups.isEmpty() ? "secp384r1" : ", secp384r1");
+        System.setProperty("jdk.tls.namedGroups", namedGroups == null || namedGroups.isEmpty() ? "secp384r1" : ", secp384r1");
 
         try {
             KEY_PAIR_GEN = KeyPairGenerator.getInstance("EC");