'No valid occurrences' raised when editing a booking

[GovernmentPlates]

Describe the bug
When editing a existing room booking, a 'no valid occurrences' is sometimes raised and prevents an edit from being saved.

To Reproduce
Steps to reproduce the behavior:

1. Create a single room booking
2. Edit said booking
3. Hit 'Save changes'
4. See error

Expected behavior
The edit to the booking should be saved.

Screenshots

[aryangupta701]

Hello could you assign this issue to me?

[ThiefMaster]

If you want to send a Pull Request you are welcome to do so. We do not assign issues to people we do not known (and it's not necessary anyway). However, unless you are somewhat familiar with Indico I don't think it'd a good first issue.