unintended double post

#### Describe the bug
Under certain conditions, a message can be sent twice unintentionally. This is pretty annoying and litters the timeline.

Roughly, this seems to happen when the app is slow, but I can't really nail it down so here are my impressions

#### To Reproduce
unclear, but ideas in no particular order
- when sharing something from another app to element, it doesn't always works as intended, can't choose the right room, go back and forth a lot, message content isnt put into the textfield and similar complications
- send message, app hangs, content is still in input field(?), push send again, message is now sent twice
- ? i'll add it when i can remember what else i was gonna say

#### Expected behavior
No way to send a message twice, even under these conditions

#### Smartphone (please complete the following information):
- Device: moto g5s+
- OS: android 10 custom rom

#### Additional context
- App version 1.1.9 F-Droid
- Homeserver: not matrix.org