glTF exporter: dont erase empty dict extras

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, 16),
+    "version": (1, 7, 17),
     'blender': (2, 91, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_export.py

@@ -106,6 +106,9 @@ def __fix_json(obj):
     if isinstance(obj, dict):
         fixed = {}
         for key, value in obj.items():
+            if key == 'extras' and value is not None:
+                fixed[key] = value
+                continue
             if not __should_include_json_value(key, value):
                 continue
             fixed[key] = __fix_json(value)