Lithuanian and Latvian documents not compilable with LyX

We provide support for the languages Lithuanian and Latvian, but they won't compile.

For Lithuanian, you need to install a special package that installs the encoding and babel support. 
But then it can still not be compiled, as we create this code:

\documentclass[lithuanian]{book}
\usepackage[l7xenc]{inputenc}
\usepackage{babel}

But as Lithuanian support is not native babel, we have to use

\documentclass{book}
\usepackage[l7xenc]{inputenc}
\usepackage[lithuanian]{babel}

Just the same as for Vietnamese. I'll provide a patch.

But can anybody tell me how to get a Latvian document to compile? I mean do you know a LaTeX-package 
that add the encoding and babel support?

thanks and regards
Uwe