Bug: Running with `--joined-members` fails

[edwinsage]

Trying to run with --joined-members fails, possibly due to avatar_url being None for some members? I'm not entirely certain. Here's the traceback.

ERROR: matrix-commander: Error during room, set, get actions. Continuing despite error. Exception: can only concatenate str (not "NoneType") to str
DEBUG: matrix-commander: Here is the traceback.
Traceback (most recent call last):
  File "/home/moist/.local/lib/python3.9/site-packages/matrix_commander/matrix_commander.py", line 6864, in action_roomsetget
    await action_joined_members(gs.client, gs.credentials)
  File "/home/moist/.local/lib/python3.9/site-packages/matrix_commander/matrix_commander.py", line 5703, in action_joined_members
    SEP
TypeError: can only concatenate str (not "NoneType") to str

[8go]

Thank you 👏 👏 👏 @edwinsage for finding the bug.
Fixed.