Visual artifacts and UI locking in Safari

[duncand]

The current CQL Runner at http://cql-runner.dataphoria.org exhibits certain visual artifacts and consequential UI failures in the Safari browser (version 11) which can be reproduced by the following steps:

1. Load the page http://cql-runner.dataphoria.org
2. Click on "Config" on the top left which brings up the config panel.
3. Click on any of the dropdown menus in that panel.
4. Click outside the config panel such as on the input window; the config panel disappears but not the dropdown menu; this is the first visual artifact.
5. Trying to click "Config" again doesn't bring that panel back.
6. Click the Run button; the Run process goes through its cycles, and when its done, the Run button has 2 triangles plus an hourglass icon all displayed at once.

Firefox and Chrome don't exhibit these problematic behaviours.