Adds check for empty topic string to avoid unecessary invalid topic e…

…rror

Signed-off-by: Jasmeet Singh <jasmeet0915@gmail.com>

src/systems/joint_state_publisher/JointStatePublisher.cc

@@ -151,9 +151,13 @@ void JointStatePublisher::PostUpdate(const UpdateInfo &_info,
  worldName = _ecm.Component<components::Name>(
  parentEntity->Data())->Data();
 
- // if topic not set it will be empty, hence invalid
+ // if topic not set it will be empty
  std::vector<std::string> topics;
- topics.push_back(this->topic);
+ // this helps avoid unecesarry invalid topic error
+ if (!this->topic.empty())
+ {
+ topics.push_back(this->topic);
+ }
  topics.push_back(std::string("/world/") + worldName + "/model/"
  + this->model.Name(_ecm) + "/joint_state");
  this->topic = validTopic(topics);