tsearch filenames unlikes special symbols and numbers

Hello

I am found small bug

postgres=# CREATE TEXT SEARCH DICTIONARY cz1(TEMPLATE = ispell,
DictFile= 'cs_czutf');
ERROR:  invalid text search configuration file name "cs_czutf"
postgres=# CREATE TEXT SEARCH DICTIONARY cz1(TEMPLATE = ispell,
DictFile= 'csczutf8');
ERROR:  invalid text search configuration file name "csczutf8"
postgres=# CREATE TEXT SEARCH DICTIONARY cz1(TEMPLATE = ispell,
DictFile= "csczutf8");
ERROR:  invalid text search configuration file name "csczutf8"
postgres=# CREATE TEXT SEARCH DICTIONARY cz1(TEMPLATE = ispell,
DictFile= "cs_czutf");
ERROR:  invalid text search configuration file name "cs_czutf"
postgres=# CREATE TEXT SEARCH DICTIONARY cz1(TEMPLATE = ispell,
DictFile= "csczutf");
ERROR:  could not open dictionary file
"/usr/local/pgsql/share/tsearch_data/csczutf.dict": není souborem ani
adresářem

regards
Pavel Stehule