`m.room.name=""` causes avatar to disappear (`avatar_url` is `null`) in DM rooms

[frebib]

Based on element-hq/element-x-android#5802

To reproduce:

1. Create a DM room
2. Observe that in the room list/room info it has the avatar of the other user in the room.
3. Send an m.room.name state event with the value "" (in EW or some client that allows doing that)
4. Notice that the room avatar disappears (might require clearing the cache)

[Hywan]

Hello,

Thanks for the report.

I wonder if the behaviour appeared since #6055. Actually, I saw your linked issue dates from November 2025, so, apparently no, it's not related.

I however think this is the expected behaviour no? The room name is set to an empty string, so… it's emptied. What do you expect?

[frebib]

This isn't a regression- it's always been the case afaik

The issue is with the room avatar, not the room name. This reliably reproduces in EXA for me

[bnjbvr]

I imagine this could be the same root cause as in #6026, where the avatar isn't set after a room rename. I wonder if the better fix for this issue and 6026 would be to make it so that we distinguish a value as undefined (= not updated) vs null (= unset). It might even be a server impl bug, or a spec issue…

[bnjbvr]

Sooo. The room avatar is updated either because there's a new m.room.avatar event in the state events, or because the inlined room info (from the room response) contains an avatar field, which can be undefined or null already. Wonder what the server sends us; it might be nice to look at the server response with a proxy, to see if it's incorrectly sending a null room avatar in this case.