Matrix no longer works with synapse 1.38

[Cadair]

Synapse is no longer returning optional fields in its sync responses, which the matrix_client library expects.

As matrix_client is no longer maintained, this would probably mean changing the library to fix. I use matrix-nio for some stuff but it's primarily async maybe something like https://gitlab.com/Swedneck/simplematrixlib would do the job.

(It should be noted that non-synapse servers haven't returned these fields for a long time)