fix automatic DM avatar with functional members

[HarHarLinks]

needed by: https://github.com/matrix-org/matrix-react-sdk/pull/12157

Checklist

• [x] Tests written for new code (and old code if feasible)
• [ ] Linter and other CI checks pass
• [x] Sign-off given on the changes (see CONTRIBUTING.md)

Signed-off-by: Kim Brose [email protected]

[HarHarLinks]

so 25fdc18 ended up reverting almost all previous changes. would you like me to squash it into all the previous ones? it should still be good to review (actually better to review in its entirety instead of incrementally) and may also be squashed when merging.

[HarHarLinks]

(not technically in scope of this Pr since it's about the avatar only, but)

with functional members, I can e.g. have a 1:1 DM between alice and frank ("Empty Room") but still search for Frank by displayname (that does not at all match their MXID) in spotlight and will still find the DM. maybe that is intentional? not sure how it does that.

[richvdh]

Don't worry about squashing, I'll just review it as-is, and we'll squash on merge.

[HarHarLinks]

Thank you for taking the time to work on this with me!