print log and throw for non standard exceptions

controller_manager/src/controller_manager.cpp

@@ -480,7 +480,7 @@ controller_interface::ControllerInterfaceBaseSharedPtr ControllerManager::load_c
  get_logger(),
  "Caught unknown exception while loading the controller '%s' of plugin type '%s'",
  controller_name.c_str(), controller_type.c_str());
- return nullptr;
+ throw;
  }
 
  ControllerSpec controller_spec;