fulltext search end with error, update of indexes crash with:

copr-frontend update_indexes

Traceback (most recent call last):
File "/usr/bin/copr-frontend", line 512, in <module>
manager.run()
File "/usr/lib/python3.6/site-packages/flask_script/init.py", line 412, in run
result = self.handle(sys.argv[0], sys.argv[1:])
File "/usr/lib/python3.6/site-packages/flask_script/init.py", line 383, in handle
res = handle(*args, config)
File "/usr/lib/python3.6/site-packages/flask_script/commands.py", line 216, in call
return self.run(*args, kwargs)
File "/usr/bin/copr-frontend", line 426, in run
index = Whooshee.get_or_create_index(app, CoprWhoosheer)
File "/usr/lib/python3.6/site-packages/flask_whooshee.py", line 382, in get_or_create_index
index = cls.create_index(app, wh)
File "/usr/lib/python3.6/site-packages/flask_whooshee.py", line 355, in create_index
if whoosh.index.exists_in(index_path):
File "/usr/lib/python3.6/site-packages/whoosh/index.py", line 136, in exists_in
ix = open_dir(dirname, indexname=indexname)
File "/usr/lib/python3.6/site-packages/whoosh/index.py", line 123, in open_dir
return FileIndex(storage, schema=schema, indexname=indexname)
File "/usr/lib/python3.6/site-packages/whoosh/index.py", line 421, in init
TOC.read(self.storage, self.indexname, schema=self._schema)
File "/usr/lib/python3.6/site-packages/whoosh/index.py", line 632, in read
check_size("int", _INT_SIZE)
File "/usr/lib/python3.6/site-packages/whoosh/index.py", line 626, in check_size
sz = stream.read_varint()
File "/usr/lib/python3.6/site-packages/whoosh/filedb/structfile.py", line 191, in read_varint
return read_varint(self.read)
File "/usr/lib/python3.6/site-packages/whoosh/util/varints.py", line 102, in read_varint
b = ord(readfn(1))
TypeError: <main.UpdateIndexesCommand object at 0x7f9841b387f0>: ord() expected a character, but string of length 0 found