Do not clear the draft if sending failed

[link2xt]

No description provided.

[link2xt]

This is needed for #4342 (see also Android issue deltachat/deltachat-android#3428), but makes sense regardless of whether sending is allowed, there may be other reasons for failing.

[WofWca]

This change makes sense to me. textareaRef is disabled until the message has been sent and the draft cleared.
Have you checked if the behavior is alright if sendMessagePromise takes some time to resolve?
Does it feel sluggish?

[nicodh]

Have you checked if the behavior is alright if sendMessagePromise takes some time to resolve?

I think we can merge this, it is very theoretical "sendMessagePromise" is fulfilled when the draft is in database. It's not waiting fpor network (I tested it)

[link2xt]

Encryption may take some time, so it is a bit slower this way, but there is nothing waiting for the network, only adding encrypted MIME message to the queue.