GLTF export fails with ZeroDivisionError
Example `.blend` file which exhibits the issue:

https://github.com/wonderunit/shot-generator-models/blob/77f39c6eac764ace508f3bf718f5443ec45a0fc6/characters/base/male-youth/male-youth.blend

Fails on this line: https://github.com/KhronosGroup/glTF-Blender-IO/blob/master/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py#L106

With the error `ZeroDivisionError: integer division or modulo by zero`

Using the nightly Blender 2.8 beta from today 7 Jan 2018.

diff --git a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
index c9c2875d..892343ea 100644
--- a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
+++ b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
@@ -107,6 +107,8 @@ def __get_image_data(sockets_or_slots, export_settings):
     # in a helper class. During generation of the glTF in the exporter these will then be combined to actual binary
     # ressources.
     def split_pixels_by_channels(image: bpy.types.Image, export_settings) -> typing.List[typing.List[float]]:
+        assert image.channels > 0, "Image '{}' has no color channels and cannot be exported.".format(image.name)
+
         channelcache = export_settings['gltf_channelcache']
         if image.name in channelcache:
             return channelcache[image.name]
['addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py']