fix: display server identity (if present) in typing indicator

[LedaThemis]

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Fixes #64

Before:

After: if there's no server identity(nickname or avatar) set, it uses user's global name and avatar.

[Rexogamer]

I think one of the blockers for this in the past was a possible memory leak - is memory usage stable after this patch?

[LedaThemis]

Memory usage looks stable,

1 Iteration

aa9974149cb4cd86ee9b53b2582cb116bc5cc1c3: 8.117MB to 8.162MB (0.045MB), 7.980MB (-0.182MB) after garbage collection. (nightly)

7f5a7aec8689c329fa970e1eecddba7c3ccfa398: 8.050MB to 8.095MB (0.045MB), 7.967MB (-0.128MB) after garbage collection.

[insertish]

I think the issue previously was with TextReact and I think I implemented a memory leak in there or something, this looks fine though.

[insertish]

Had to revert, I was merging PRs quite quickly so I missed this issue entirely: this does not consider situations where member objects are not available (may not have synced) or if we're in a DM (no server).