Room Directory and Chat with Riot Biot from welcome broken when HS disables guest access

[jryans]

If the default HS for your Riot install has guest access disabled (allow_guest_access: False), then both the "Chat with Riot Bot" and "Room Directory" actions will fail quite badly:

• Chat with Riot Bot silently does nothing
• Room Directory opens a model an infinite spinner:

[turt2live]

We should just hide these options when we can't register a guest imo

Or provide a config option to hide the whole section.