Selecting text in composer and using the onscreen backspace button only deletes part of the message.

This is happening with AOSP keyboard, haven't tested another keyboard yet.

Steps to reproduce:

1. Enter a room, type a message consisting of a few words. I.e. "Test message one two three. Hello." (It might be important to type and not paste it.)
2. Leave the room
3. Enter room again, the message draft is now there.
4. Long press and drag over the full message to select it.
5. Type `backspace`

On my phone this randomly deletes only (some prefix) part of the message or once even nothing at all. It seems to respect word boundaries.

I.e. with the above test message you might be left with the following text in your composer (it's not selected anymore): "two three. Hello."