fix a crash

Author: moehreag

src/main/java/io/github/axolotlclient/modules/rpc/DiscordRPC.java

@@ -132,9 +132,14 @@ public void updateActivity() {
     }
 
     public static void setWorld(String world){
-        currentActivity.setDetails("World: "+ world);
-        if(discordRPC.isOpen()) {
-            discordRPC.activityManager().updateActivity(currentActivity);
+        if(running) {
+            if (currentActivity == null) {
+                DiscordRPC.getInstance().updateRPC();
+            }
+            currentActivity.setDetails("World: " + world);
+            if (discordRPC.isOpen()) {
+                discordRPC.activityManager().updateActivity(currentActivity);
+            }
         }
     }