Fix Grid IPP selector

[mkrecek234]

fix #2016

[mvorisek]

needs a Behat test and explanation why set should be done using string, also do not forget, IPP must be definitely typecasted with UI persistence :)

[mkrecek234]

@mvorisek Even if you raised now the bar to enforce behat tests, I cannot provide this, as it drives efforts to fix newly introduced bugs significantly, even though the fix is simply like in this case. This bug is really annoying, as it destroys the IPP functionality simply. So I would welcome either a merge by you, or any contribution by you to make it ready-to-merge also based on your lifted requirements.

[mvorisek]

Michael, adding a Behat test is not so complicated, but it is needed to prevent such bug from happening again.

Also please understand the fix is not correct as explained in my post above.

[mvorisek]

Thank you @mkrecek234, no one can break it now :)