coloring volume surf gives TypeError unsupported operand type(s) for +=: 'NoneType' and 'int'

[Elaine Meng]

Coloring an isosurfaces gives error:

color #2 purple
Traceback (most recent call last):
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/cmd_line/tool.py", line 201, in execute
cmd.run(cmd_text)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/commands/cli.py", line 2550, in run
result = ci.function(session, kw_args)
File "/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/commands/color.py", line 159, in color
ns += len(mlist)
TypeError: unsupported operand type(s) for +=: 'NoneType' and 'int'

[Elaine Meng]

At first I blamed previous bump-coloring but now I see that simply opening a volume and then changing its color causes the error. Coloring molecular surface does not have this problem.

[Elaine Meng]

Actually coloring molscular surface can have this problem. Haven't figured out the prerequisites but opening the attached coloring command file seems to do it reliably.

[Tom Goddard]

Fixed.

I fixed this yesterday but forgot to git push the changes. The bug was introduced when I changed molecular surfaces to remember atom colors 2 days ago.