Fix crash when opening rooms where the current user doesn't have perm…

[stefanceriu]

…ission to post messages.

[github-actions]

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[aringenbach]

LGTM but I wonder if we should rather use
inputToolbarViewAsRoomInputToolbarView
everywhere on RoomViewController.

I did not try to reproduce, but it seems to me that this kind of cast might succeed on the disabled version, hence the crash :
RoomInputToolbarView *inputToolbar = (RoomInputToolbarView *)self.inputToolbarView;

[stefanceriu]

Well the code around this whole thing, while an absolute mess, does usually check using isKindOfClass:RoomInputToolbarView. I wouldn't spend more time on this than absolutely necessary, nothing good can come out of it without a full rewrite ¯_(ツ)_/¯