Catch exceptions when creating publishers in tools

[rhaschke]

Fix #1466: An invalid ros topic name caused rviz to crash due to the uncaught exception.

[simonschmeisser]

even more fancy would be showing some visual feedback :)

[rhaschke]

For now, this needs to be sufficient. I don't have the (time) resources to provide visual feedback now.
I thought about indicating an error via a red background in the input field. But this will involve ABI changes: properties need to have an additional boolean flag to indicate the error condition. Then getViewData() can return the corresponding background color. Probably, it would be great to provide the error message as well, e.g. as a tooltip.