[bugtracker] Add extra membergroups to manage blocks does not save the action you choose

[G6Cad]

Choose your extra membergroups that can edit this block only.

Note that "manage_blocks" and "admin" permission always give this right regardless.

This option inside block administration does not save the checks you add for the membergroups.
It reverse to previous empty catboxes when you save your choices.

Tested on SMF 1.1.6 tp v1 beta 2 and 3  and SMF 1.1.7 TP1 beta 2 and 3

[bloc]

- Missing code did not save the option for allowed membergroups on blocks.Fixed for TP 1.0 beta3