fix(actionlib): Remove getState error when no goal is running

[alireza-hosseini]

As explained in #40 in many situations the developer needs to know if the action client is tracking a goal or not which is possible by the getState method of the SimpleActionClient. But the problem is, using this function while the action client didn't send any goal before, results to the following error:

Trying to getState() when no goal is running. You are incorrectly using SimpleActionClient

This PR simply removes this ROS error since it's not really an incorrect usage of the SimpleActionClient (closes #40).

[alireza-hosseini]

I checked the Jenkins report for the failed jobs, apparently, they are not related to my changes.

[alireza-hosseini]

Is there any plan to review this simple PR?

[jschleicher]

Looks good to me. @mikaelarguedas Could you please review and merge this change?

[mikaelarguedas]

@alireza-hosseini @jschleicher This looks good to me, I agree it's not really an invalid usage of the simple action client.
I originally held this as I was planning on releasing it only for ROS Melodic to not change behavior for people that may be expecting these logging messages.

I'll leave it up to the current maintainer to review / merge / release but you have my 👍

[jschleicher]

@mikaelarguedas merging this for kinetic onwards would be fine for me. On the other hand this logging message shouldn't break any existing code (and is ABI compatible of course).

Who is the current maintainer?

[mikaelarguedas]

On the other hand this logging message shouldn't break any existing code (and is ABI compatible of course).

agreed 👍

Who is the current maintainer?

@mjcarroll is the current maintainer

[mjcarroll]

LGTM, thanks for the contribution.