Fix minor sonarlint issues

Author: nightowlengineer

src/main/java/engineer/nightowl/sonos/api/SonosApiClient.java

@@ -22,7 +22,6 @@
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
-import java.net.http.HttpClient;
 import java.util.Properties;
 
 public class SonosApiClient implements AutoCloseable

src/main/java/engineer/nightowl/sonos/api/resource/GroupResource.java

@@ -93,11 +93,11 @@ public SonosGroupInfo modifyGroupMembers(final String clientToken, final String
                                              final List<String> playerIdsToRemove) throws SonosApiClientException, SonosApiError
     {
         final Map<String, Object> payload = new HashMap<>();
-        if (playerIdsToAdd != null && playerIdsToAdd.size() > 0)
+        if (playerIdsToAdd != null && !playerIdsToAdd.isEmpty())
         {
             payload.put("playerIdsToAdd", playerIdsToAdd);
         }
-        if (playerIdsToRemove != null && playerIdsToRemove.size() > 0)
+        if (playerIdsToRemove != null && !playerIdsToRemove.isEmpty())
         {
             payload.put("playerIdsToRemove", playerIdsToRemove);
         }