How to fix in .htaccess?

Question

htaccess

There is such a line in htaccess:
RewriteRule ^(ua|ru|)?/?(.*)$ $2?lang=$1
It finds out what language the user has requested and already gives out the information he needs.
There is a problem
1: mysite.com/ua - it works
2. mysite.com/ru - it works
3. mysite.com/zdes_chto_nibyd - then I get an Internal Server Error, can I somehow assign a value that is not necessary to ru or ua?
Thanks in advance.

Answer 1

whole file here