Python exception when exporting NLA tracks while editing an NLA track

[sjkillen]

Describe the bug
Exporting while editing an animation in an NLA track produces an error

To Reproduce
Steps to reproduce the behavior:

1. Create mesh with rig
2. Create an NLA track with simple animation
3. Click the animation in the track and press tab to edit it.
4. Export with export_animation_mode="NLA_TRACKS"
5. See error

.blend file/ .gltf (mandatory)

issue.zip

Open file and run included script from text window

Version

- OS: Linux
- Blender Version: 4.4 alpha (47bc05f7ae59)

Additional context
Resulting error:

Read blend: "/home/rat/Downloads/issue/Untitled.blend"
INFO Draco mesh compression is available, use library at /home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/libextern_draco.so
19:57:20 | INFO: Starting glTF 2.0 export
19:57:20 | INFO: Extracting primitive: Cube
19:57:20 | INFO: Primitives created: 1
Traceback (most recent call last):
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/__init__.py", line 1356, in execute
    res = gltf2_blender_export.save(context, export_settings)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 37, in save
    json, buffer = __export(export_settings)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 55, in __export
    __gather_gltf(exporter, export_settings)
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 202, in __gather_gltf
    active_scene_idx, scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/gather.py", line 35, in gather_gltf2
    animations += gather_animations(export_settings)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/animations.py", line 22, in gather_animations
    return gather_tracks_animations(export_settings)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/tracks.py", line 69, in gather_tracks_animations
    animations_, merged_tracks = gather_track_animations(obj_uuid, merged_tracks, len(animations), export_settings)
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/tracks.py", line 150, in gather_track_animations
    blender_object.animation_data.action = None
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: bpy_struct: attribute "action" from "AnimData" is read-only
Error: Python: Traceback (most recent call last):
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/__init__.py", line 1356, in execute
    res = gltf2_blender_export.save(context, export_settings)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 37, in save
    json, buffer = __export(export_settings)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 55, in __export
    __gather_gltf(exporter, export_settings)
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 202, in __gather_gltf
    active_scene_idx, scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
                                           ^^^^^^^^^^^^^^^^^^^^^Error: Python: Traceback (most recent call last):
  File "/home/rat/Downloads/issue/Untitled.blend/Text", line 3, in <module>
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/modules/bpy/ops.py", line 109, in __call__
    ret = _op_call(self.idname_py(), kw)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: Error: Python: Traceback (most recent call last):
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/__init__.py", line 1356, in execute
    res = gltf2_blender_export.save(context, export_settings)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 37, in save
    json, buffer = __export(export_settings)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 55, in __export
    __gather_gltf(exporter, export_settings)
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/export.py", line 202, in __gather_gltf
    active_scene_idx, scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/gather.py", line 35, in gather_gltf2
    animations += gather_animations(export_settings)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/animations.py", line 22, in gather_animations
    return gather_tracks_animations(export_settings)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/tracks.py", line 69, in gather_tracks_animations
    animations_, merged_tracks = gather_track_animations(obj_uuid, merged_tracks, len(animations), export_settings)
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rat/blender-git/build_linux_full/bin/4.4/scripts/addons_core/io_scene_gltf2/blender/exp/animation/tracks.py", line 150, in gather_track_animations
    blender_object.animation_data.action = None
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: bpy_struct: attribute "action" from "AnimData" is read-only
Location: /home/rat/blender-git/build_linux_full/bin/4.4/scripts/modules/bpy/ops.py:109

[julienduroure]

Confirmed.
The tweak mode check that is done on Action mode is not implement for NLA Track mode.

(Note that Action mode also crash for now, for a not related reason)