hiscore client: check response code of hiscore lookups

http-api/src/main/java/net/runelite/http/api/hiscore/HiscoreClient.java

@@ -56,6 +56,12 @@ public class HiscoreClient
 
 		try (Response response = RuneLiteAPI.CLIENT.newCall(request).execute())
 		{
+			if (!response.isSuccessful())
+			{
+				logger.debug("unsuccessful lookup for {}", username);
+				return null;
+			}
+
 			InputStream in = response.body().byteStream();
 			return RuneLiteAPI.GSON.fromJson(new InputStreamReader(in), HiscoreResult.class);
 		}
@@ -88,6 +94,12 @@ public class HiscoreClient
 
 		try (Response response = RuneLiteAPI.CLIENT.newCall(request).execute())
 		{
+			if (!response.isSuccessful())
+			{
+				logger.debug("unsuccessful lookup for {}", username);
+				return null;
+			}
+
 			InputStream in = response.body().byteStream();
 			return RuneLiteAPI.GSON.fromJson(new InputStreamReader(in), SingleHiscoreSkillResult.class);
 		}

runelite-client/src/main/java/net/runelite/client/plugins/hiscore/HiscorePanel.java

@@ -413,11 +413,7 @@ public class HiscorePanel extends PluginPanel
 			return;
 		}
 
-		/*
-		For some reason, the fetch results would sometimes return a not null object
-		with all null attributes, to check for that, i'll just null check one of the attributes.
-		 */
-		if (result == null || result.getAttack() == null)
+		if (result == null)
 		{
 			input.setIcon(ERROR_ICON);
 			input.setEditable(true);