'NoneType' object has no attribute 'yabee_name'

[The-Golden-Rose]

Using YABEE on Blender 2.7.4. I've used this to make EGG files of stagnant and animated models before, but today I'm trying to animate a cube to "wave" like water, with the armature looking like the following:

However, trying to export this cube as an animated EGG file is giving a pop up of "export failed, check console for details," and the console showing the following error:

Traceback (most recent call last):
  File "C:\Users\...\Blender\2.74\scripts\addons\YABEE-master\yabee_libs\egg_writer.py", line 1719, in write_out
    print('Objects for export:', [obj.yabee_name for obj in obj_list])
  File "C:\Users\...\Blender\2.74\scripts\addons\YABEE-master\yabee_libs\egg_writer.py", line 1719, in <listcomp>
    print('Objects for export:', [obj.yabee_name for obj in obj_list
AttributeError: 'NoneType' object has no attribute 'yabee_name'

This is the first time I've tried to make an animated EGG on this computer, but I've used this add-on on Blender 2.7.4 on other machines to make animated EGG files and have never seen this before.

Any idea what's happening here?