Save multimodel PDB error

[Tom Goddard]

open 1r7z
save test[ID].pdb model #1

Traceback (most recent call last):
File "/Users/goddard/ucsf/chimerax/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/cmd_line/tool.py", line 178, in execute
cmd.run(cmd_text)
File "/Users/goddard/ucsf/chimerax/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/commands/cli.py", line 2390, in run
result = ci.function(session, kw_args)
File "/Users/goddard/ucsf/chimerax/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/commands/save.py", line 58, in save
fmt.export(session, filename, fmt.nicknames[0], kw)
File "/Users/goddard/ucsf/chimerax/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/io.py", line 168, in export
result = self.export_func(*args, kw)
File "/Users/goddard/ucsf/chimerax/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/chimerax/core/atomic/pdb.py", line 82, in save_pdb
pdbio.write_pdb_file([m.cpp_pointer], file_name, selected_only=selected_only,
AttributeError: 'Model' object has no attribute 'cpp_pointer'

[pett]

Same problem as #758