Null-check WorldResult in DefaultWorldPlugin

Closes #8043

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

runelite-client/src/main/java/net/runelite/client/plugins/defaultworld/DefaultWorldPlugin.java

@@ -114,6 +114,13 @@ public class DefaultWorldPlugin extends Plugin
 		try
 		{
 			final WorldResult worldResult = worldClient.lookupWorlds();
+
+			if (worldResult == null)
+			{
+				log.warn("Failed to lookup worlds.");
+				return;
+			}
+
 			final World world = worldResult.findWorld(correctedWorld);
 
 			if (world != null)