glTF exporter: fix animation export when no channels are valid

io_scene_gltf2/__init__.py

@@ -15,7 +15,7 @@
 bl_info = {
     'name': 'glTF 2.0 format',
     'author': 'Julien Duroure, Scurest, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein, and many external contributors',
-    "version": (1, 7, 22),
+    "version": (1, 7, 23),
     'blender': (2, 91, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_animation_channels.py

@@ -118,7 +118,8 @@ def gather_animation_channels(blender_action: bpy.types.Action,
                 blender_action.name,
                 obj,
                 False)
-            channels.append(channel)
+            if channel is not None:
+                channels.append(channel)
 
     else:
         for channel_group in __get_channel_groups(blender_action, blender_object, export_settings):

io_scene_gltf2/blender/exp/gltf2_blender_gather_animations.py

@@ -121,12 +121,12 @@ def __gather_animation(blender_action: bpy.types.Action,
         print_console("WARNING", "Animation '{}' could not be exported. Cause: {}".format(name, error))
         return None
 
-    # To allow reuse of samplers in one animation,
-    __link_samplers(animation, export_settings)
-
     if not animation.channels:
         return None
 
+    # To allow reuse of samplers in one animation,
+    __link_samplers(animation, export_settings)
+
     export_user_extensions('gather_animation_hook', export_settings, animation, blender_action, blender_object)
 
     return animation