Unable to register if car registration isn't modified

[jernejk]

Describe the bug Attempting to register at https://portal.brisbanemaker.space/register without filling out the vehicle registration will result in a null ref on validation.

To Reproduce Steps to reproduce the behavior:

1. Go to https://portal.brisbanemaker.space/register
2. Fill out the form without touching the vehicle registration
3. Click on Submit
4. See error in F12

Expected behavior We should be able to register without needing to enter optional fields.

Desktop (please complete the following information):

• OS: Windows 11
• Browser: Edge and FireFox

Smartphone (please complete the following information):

• Device: Samsung Galaxy S21+
• OS: Android
• Browser: Chrome

Additional context If vehicle registration is not set, the value on line 29 in file formMixin.ts will throw a null reference exception.

I think the code fix would be: return !value || value.toString().length <= 30;

But I'm a bit rusty on TS/React.