check empty plugins, update issue url

Signed-off-by: Ian Chen <[email protected]>

Author: iche033

src/SystemManager.cc

@@ -220,6 +220,13 @@ void SystemManager::ProcessPendingEntitySystems()
   {
     Entity entity = req.entity().id();
 
+    if (req.plugins().empty())
+    {
+      ignerr << "Unable to add plugins to Entity: '" << entity
+             << "'. No plugins specified." << std::endl;
+       continue;
+    }
+
     for (auto &pluginMsg : req.plugins())
     {
       std::string fname = pluginMsg.filename();
@@ -231,5 +238,3 @@ void SystemManager::ProcessPendingEntitySystems()
   }
   this->systemsToAdd.clear();
 }
-
-

test/integration/entity_system.cc

@@ -149,7 +149,7 @@ class EntitySystemTest : public InternalFixture<::testing::TestWithParam<int>>
 };
 
 /////////////////////////////////////////////////
-// See https://github.com/ignitionrobotics/ign-gazebo/issues/1175
+// See https://github.com/gazebosim/gz-sim/issues/1175
 TEST_P(EntitySystemTest, IGN_UTILS_TEST_DISABLED_ON_WIN32(PublishCmd))
 {
   TestPublishCmd(