Repository: khronosgroup/gltf-blender-io
Issue: I can not export animation from Blender to glTF

**Describe the bug**
When I export without animation it do it correctly. But with animation it gives this error:

```
Python: Traceback (most recent call last):
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\__init__.py", line 628, in execute
    return gltf2_blender_export.save(context, export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_export.py", line 35, in save
    json, buffer = __export(export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_export.py", line 52, in __export
    __gather_gltf(exporter, export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_export.py", line 66, in __gather_gltf
    active_scene_idx, scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather.py", line 34, in gather_gltf2
    animations += __gather_animations(blender_scene, export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather.py", line 91, in __gather_animations
    animations_, merged_tracks = gltf2_blender_gather_animations.gather_animations(obj_uuid, merged_tracks, len(animations), export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animations.py", line 128, in gather_animations
    animation = __gather_animation(obj_uuid, blender_action, export_settings)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animations.py", line 171, in __gather_animation
    channels=__gather_channels(obj_uuid, blender_action, export_settings),
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animations.py", line 208, in __gather_channels
    return gltf2_blender_gather_animation_channels.gather_animation_channels(
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_cache.py", line 38, in wrapper_cached
    result = func(*args, **kwargs)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animation_channels.py", line 106, in gather_animation_channels
    channel = gather_animation_channel(
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animation_channels.py", line 266, in gather_animation_channel
    __target= __gather_target(obj_uuid, channels, export_settings, bake_bone, bake_channel, driver_obj_uuid)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animation_channels.py", line 359, in __gather_target
    return gltf2_blender_gather_animation_channel_target.gather_animation_channel_target(
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_cache.py", line 38, in wrapper_cached
    result = func(*args, **kwargs)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animation_channel_target.py", line 29, in gather_animation_channel_target
    path=__gather_path(channels, blender_object, export_settings, bake_bone, bake_channel)
  File "C:\\Program Files\\Blender Foundation\\Blender 3.2\\3.2\\scripts\\addons\\io_scene_gltf2\\blender\\exp\\gltf2_blender_gather_animation_channel_target.py", line 92, in __gather_path
    target = [c for c in channels if c is not None][0].data_path.split('.')[-1]
IndexError: list index out of range
```


**To Reproduce**
Steps to reproduce the behavior:
1. Export glTF.
2. The Error.

**Expected behavior**
It should be exported!

**Screenshots**
https://prnt.sc/Nurs4KGP_3sQ

**.blend file/ .gltf**
[If applicable, a zipped folder containing a .blend file for exporter issues and a .gltf file for importer issues. Please take care to include all resources, such as textures in the .zip file.](https://drive.google.com/file/d/1z6ItwiDhCnXrbXcUl2QorORm7g7xeLtL/view?usp=sharing)

**Version**
 - Windows 10 x64
 - Blender Version 3.2.1
 
**Additional context**
In 2.91 version was the same error

Changed files:
addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py

diff --git a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py
index e3232b99..4166a5e1 100644
--- a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py
+++ b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py
@@ -85,7 +85,8 @@ def get_sk_drivers(blender_armature_uuid, export_settings):
             else:
                 all_sorted_channels.append(existing_idx[i])
 
-        if len(all_sorted_channels) > 0:
+        # Checks there are some driver on SK, and that there is not only invalid drivers
+        if len(all_sorted_channels) > 0 and not all([i is None for i in all_sorted_channels]):
             drivers.append((child_uuid, tuple(all_sorted_channels)))
 
     return tuple(drivers)