Limit depth of _boost_mkdir_p function

I've installed Boost in a new drupal installation.
In admin/settings/performance/boost form I've checked "Do not store the cache file path in the database"; when I've clicked on Submit button, I've got "maximum number of 100 function reached" error.
The issue is in boost_admin_boost_performance_page_validate because in this case, $boost_file_path variable is an empty string, so _boost_mkdir_p called with this var as argument going in an infinite loop.
If all wrote above is right, can you modify _boost_mkdir_p to avoid loops or add a condition to boost_admin_boost_performance_page_validate.
Tnx a lot
Corrado