Impossible to un-react to a message

#### Describe the bug.
When adding a reaction to a message, it can become impossible to un-react

#### Steps to reproduce:
Steps to reproduce the behavior:
1. Go to a room and add a reaction to a message
2. Get back to room list view
3. Get back to the room you were in
4. The reaction is not highlighted (as if you never had reacted), and tapping it doesn't to anything

#### Expected behavior
The app should highlight my reaction, and I should be able to un-react

#### Contextual information:
- Device: iPhone 11 Pro
- OS: iOS 14.7.1
- App Version: Element 1.5.1 (build 20210812163331 from TestFlight)