Comment 4 for bug 1945881

Unhandled exception in state: State: _job_done Client: myip:43860 Request: GET /interface-data/tag-browser?collapse_at=25&hide_empty_categories=no&library_id=Library&partition_method=partition&sort_tags_by=name HTTP/1.1
Traceback (most recent call last):
  File "calibre\srv\loop.py", line 621, in tick
  File "calibre\srv\loop.py", line 345, in _job_done
  File "calibre\srv\http_response.py", line 505, in job_done
  File "calibre\srv\http_response.py", line 677, in finalize_output
  File "calibre\srv\http_response.py", line 354, in __call__
  File "calibre\srv\code.py", line 397, in generate
  File "calibre\srv\metadata.py", line 542, in categories_as_json
  File "calibre\srv\handler.py", line 150, in get_tag_browser
  File "calibre\srv\metadata.py", line 528, in render_categories
  File "calibre\srv\metadata.py", line 497, in fillout_tree
  File "calibre\srv\metadata.py", line 406, in process_category_node
  File "calibre\srv\metadata.py", line 336, in collapse_partition
AttributeError: 'dict' object has no attribute 'category'