Hi Nicolas,
Sure! That code section is similar for both plugins, and the issue was discovered by you, so it is not yet fixed in the Pro version either. The fix is almost identical:
(make a backup first)
1. Look for the wp-content/plugins/ajax-search-pro/includes/classes/etc/class-asp_helpers.php file
2. Replace it’s contents with this
3. Save
Hopefully all goes well and this will work.