ginga: crash after trying to create thumbs

I put the crash report here: https://gist.github.com/michaelaye/5342b311d55d2cab619951064d06589e

I tried to create thumbs for approx 10-15 fits.gz image via the file browser interface.

Note that I pressed the “Make thumbs” twice more after I saw the icon de-color the first time without seeing any output anywhere. I was assuming that the decolorization of the Make thumbs icon means that the processing is done? Maybe I was too impatient?

Using 766c1275ab50d24 of ginga on macOS 10.11.6, installed from GH master on top of a python 3.5 env cultivated by conda. 😉