mod_invites_adhoc: Set non-nil defaults for options, fixes traceback (thanks Martin)
Fixes an error when attempting to call the :empty() method on the
default implicit default nil value.
# Introduction
This module adds a room configuration option to hide inline media from
unaffiliated users in MUCs and display them as links instead.
This can be useful in public channels where content posted by users should not
be shown by default.
# Configuring
## Enabling
``` {.lua}
Component "rooms.example.net" "muc"
modules_enabled = {
"muc_restrict_media";
}
```
## Settings
A default setting can be provided in the config file:
``` {.lua}
muc_room_default_restrict_media = true
```