can't autocomplete in a command line

[AmandineLP]

if I type '/me asks tom' and tries to autocomplete 'tom' the autocomplete is still about the /me command, despite having other words in the middle

[lampholder]

I think this is a dup of #6993 - this looks like it's a regression we introduced on the draft.js-backed composer, which now also (and independently?) exists on the slate.js-backed composer

[t3chguy]

This should have been fixed (for /me) by matrix-org/matrix-react-sdk#2074 but due to a double-negative typo it was not, it will be fixed in the upcoming Slate fixes PR as its somewhat related but yes in other commands #6993 is the issue