id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	blockedby	blocking	notify_on_close	platform	project
1756	hide/show DICOM SEG gives AttributeError: 'NoneType' object has no attribute 'redraw_needed'	Elaine Meng	Tom Goddard	"
Platform:        Darwin-17.7.0-x86_64-i386-64bit
ChimeraX Version: 0.9 (2019-03-07)

Description
With the dataset that includes a CT scan and associated SEG models, showing/hiding the SEG models (e.g. with checkboxes in the Model Panel) gives a traceback.  Example dataset 
https://www.rbvi.ucsf.edu/chimerax/data/dicom/11-06-2014-1-96508-subset.zip

Log:

> open /Users/meng/Desktop/11*subset* format dicom

Opened multi-channel map CHEST CT 4, 4 channels, grid size 512,512,236, pixel
0.576,0.576,1.25, shown at step 1, values int16  

> show #!1.1.1.1.4 models

Exception ignored in: <function Drawing.__del__ at 0x10c5e9d90>  
Traceback (most recent call last):  
File
""/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-
packages/chimerax/core/graphics/drawing.py"", line 1086, in __del__  
self.delete()  
File
""/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-
packages/chimerax/map/image3d.py"", line 618, in delete  
ir._remove_planes()  
File
""/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-
packages/chimerax/map/image3d.py"", line 532, in _remove_planes  
self._drawing.redraw_needed()  
AttributeError: 'NoneType' object has no attribute 'redraw_needed'  


OpenGL version: 4.1 NVIDIA-10.32.0 355.11.10.10.40.102
OpenGL renderer: NVIDIA GeForce GTX 675MX OpenGL Engine
OpenGL vendor: NVIDIA Corporation

"	defect	assigned	normal		Volume Data								all	ChimeraX