error saving model image

[Greg Couch]

When opening 1tna, I get the following traceback:

Opened mmCIF data containing 1652 atoms and 1770 bonds
Error processing trigger "frame drawn"
Traceback (most recent call last):
File "C:\cygwin64\home\gregc\src\chimerax\ChimeraX.app\bin\lib\site-packages\chimerax\core\triggerset.py", line 114, in invoke
return self._func(self._name, data)
File "C:\cygwin64\home\gregc\src\chimerax\ChimeraX.app\bin\lib\site-packages\chimerax\core\filehistory.py", line 49, in <lambda>
t.add_handler('frame drawn', lambda *args, s=self: s.capture_thumbnails_cb())
File "C:\cygwin64\home\gregc\src\chimerax\ChimeraX.app\bin\lib\site-packages\chimerax\core\filehistory.py", line 61, in capture_thumbnails_cb
fs.capture_image(models, ses)
File "C:\cygwin64\home\gregc\src\chimerax\ChimeraX.app\bin\lib\site-packages\chimerax\core\filehistory.py", line 120, in capture_image
self.image = models_image(session, models, size)
File "C:\cygwin64\home\gregc\src\chimerax\ChimeraX.app\bin\lib\site-packages\chimerax\core\filehistory.py", line 166, in models_image
image.save(img_io, format=format)
AttributeError: 'NoneType' object has no attribute 'save'

[Tom Goddard]

Fixed.

Initial display of 1tna.cif shows nothing and that caused trouble for the file history image thumbnail code.