glTF exporter: fix crash when trying to export some muted driver(s)

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, 19),
+    "version": (1, 7, 20),
     'blender': (2, 91, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_drivers.py

@@ -56,6 +56,9 @@ def get_sk_drivers(blender_armature):
                 sk_name = child.data.shape_keys.path_resolve(get_target_object_path(sk_c.data_path)).name
             except:
                 continue
+            # Do not take into account this driver if corresponding SK is disabled
+            if child.data.shape_keys.key_blocks[sk_name].mute is True:
+                continue
             idx = shapekeys_idx[sk_name]
             idx_channel_mapping.append((shapekeys_idx[sk_name], sk_c))
         existing_idx = dict(idx_channel_mapping)
@@ -65,7 +68,8 @@ def get_sk_drivers(blender_armature):
             else:
                 all_sorted_channels.append(existing_idx[i])
 
-        drivers.append((child, tuple(all_sorted_channels)))
+        if len(all_sorted_channels) > 0:
+            drivers.append((child, tuple(all_sorted_channels)))
 
     return tuple(drivers)