Fixes exception UninitializedStaticallyTypedParameterException when declaring a parameter without default value

[JafarAbdi]

Maybe I should push it upstream to replace https://github.com/ros2/rclcpp/blob/master/rclcpp/include/rclcpp/node_impl.hpp#L220-L232

[JafarAbdi]

I'll wait on somebody else to approve this one. It seems like a lot of added code just to fix a nitpicky compiler warning, if I understand right.

It's an exception not a warning, I updated the title