Merge pull request #5647 from RosettaCommons/roccomoretti/fix_noisy_selection_mode
[Foldit] Hotfix issue with clicking in Selection Mode.
This PR is intended as a hotfix for the currently pending release.
There was a bug where clicking any non-ligand-designable position (even in puzzles without ligand design) would show an error message from ligand design mode. This PR suppresses that error message, and only makes the relevant code happen when ligand design is active.
(The message was too chatty anyway - we actually don't need to popup. Doing nothing is feedback enough, as if you can do something, it will display a highlighted atom.)