projects crash if glyphs are missing from a font

[shadoof]

• we should report this as a warning and prevent the crash
• we will need a list of glyphs for the default "BFont" file, which I plan to encourage students to use in the first instance
• to reproduce: 1) put a 'pipe' or a 'bullet' character (option-8 on a Mac) into the text field of a text object, 2) leave the font field blank, 3) attempt to preview the project

[shadoof]

INVOCATION >> /Users/kongqi/W3D/blender/blender.app/Contents/MacOS/blender --background --python /Users/kongqi/W3D/Writing3D/scripts/Mac/../../samples/cwapp.py -- desktop /Users/kongqi/GDrive/BrownGDrive2013/Courses/Writing3D/Writing3D_XML_Samples/sample_00_random.xml found bundled python: /Users/kongqi/W3D/blender/blender.app/Contents/MacOS/../Resources/2.76/python W3D Configuration loaded from /Users/kongqi/.w3d.json Configuration information: {'Export script path': '/Users/kongqi/W3D/Writing3D/pyw3d/w3d_export_tools.py', 'Blender executable': '/Users/kongqi/W3D/blender/blender.app/Contents/MacOS/blender', 'Blender player executable': '/Users/kongqi/W3D/blender/blenderplayer.app/Contents/MacOS/blenderplayer'} Traceback (most recent call last): File "/Users/kongqi/W3D/Writing3D/scripts/Mac/../../samples/cwapp.py", line 67, in fullscreen=(args.config == "desktopfull") File "/Users/kongqi/W3D/Writing3D/pyw3d/w3d_export_tools.py", line 51, in export_to_blender input_project.blend() File "/Users/kongqi/W3D/Writing3D/pyw3d/project.py", line 553, in blend self._blend() File "/Users/kongqi/W3D/Writing3D/pyw3d/project.py", line 588, in blend object.blend() File "/Users/kongqi/W3D/Writing3D/pyw3d/objects.py", line 1082, in blend blender_object = self["content"].blend() File "/Users/kongqi/W3D/Writing3D/pyw3d/objects.py", line 610, in blend apply_euler_rotation(final_object, math.pi / 2, 0, 0) File "/Users/kongqi/W3D/Writing3D/pyw3d/objects.py", line 69, in apply_euler_rotation blender_object.data.transform( AttributeError: 'NoneType' object has no attribute 'transform'

[wphicks]

Possibly related to #78.

[wphicks]

Note to self: Probably best to just drop an empty into the scene when this happens. No other default seems sensible.