[LEDE-DEV] Fix of uci show (and similar) when /etc/config contains subdirectories

[Michal 'vorner' Vaner]

Hello

It was pointed to me by a user that when the /etc/config contains
subdirectories, uci show lists everything only up to the first subdirectory and
then stops.

It turns out the uci_list_config_files returns an array which has holes (NULLs)
in places of the subdirectories, as it tries to filter them out. Would it be
possible to apply this?

Thank you