Behaviours - setRequired method for Tempo Account and Teams Field allows you to submit the value None

Behaviours setRequired method treats the None value in the Tempo Account field as a valid value and allows the submition of the issue. This is because Tempo set the value to the string "-1" rather than null or empty.

How to reproduce:
1. Install any Tempo plugin (e.g. Tempo Timesheets)
2. Add new Tempo Account, link it with any project
3. Add account field on creation screen of any issue type in that project
4. Create new Behaviours, mappings for that project/issue type combo mentioned earlier
5. Add Initialiser with this code getFieldByName("Account").setRequired(true)
6. Try to Create issue - in dialog window, the Account field will have a red star and will look like required, but if you select "None" for Account field, the issue will still be created