glTF exporter: sanity check that action has channels when sampling animation

io_scene_gltf2/__init__.py

@@ -15,7 +15,7 @@
 bl_info = {
     'name': 'glTF 2.0 format',
     'author': 'Julien Duroure, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein, and many external contributors',
-    "version": (0, 9, 72),
+    "version": (0, 9, 73),
     'blender': (2, 81, 6),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_channels.py

@@ -52,6 +52,10 @@ def gather_animation_channels(blender_action: bpy.types.Action,
     if blender_object.type == "ARMATURE" and export_settings['gltf_force_sampling'] is True:
         # We have to store sampled animation data for every deformation bones
 
+        # Check that there are some anim in this action
+        if bake_range_start is None:
+            return []
+            
         # Then bake all bones
         for bone in blender_object.data.bones:
             for p in ["location", "rotation_quaternion", "scale"]: