runelite: fix check for client before requesting itemmanager

If outdated, this.client is null but client is not null. Invoking get() on the item manager provider will make guice late construct it and it has a dependency on client.

runelite-client/src/main/java/net/runelite/client/RuneLite.java

@@ -176,7 +176,7 @@ public class RuneLite
 		eventBus.register(commandManager);
 		eventBus.register(pluginManager);
 		eventBus.register(clanManager);
-		if (client != null)
+		if (this.client != null)
 		{
 			eventBus.register(itemManager.get());
 		}