Product details item groups read property on null fix

[wittman]

Description

Product details item groups read property on null fix.

$groups->getFirst() can return null which was not guarded against.

Sentry error caught access on null: $groups->getFirst()->item_group (line 1134).

If null there are zero groups.

Testing Instructions

Checkout PR in store working dir.

With pnpm start --symlinks=store...

Checkout coursehost master working dir.

https://berna.silverorange.com/course-host-ccme/work-USERNAME/www/admin/Product/Details?id=78 should return the UI without any exception errors.

Developer Checklist

Before requesting review for this PR, make sure the following tasks are
complete:

• I added a link to the relevant Shortcut story, if applicable
• I added testing instructions, if any
• I made sure existing CI checks pass
• I checked that all requirements of the ticket are fulfilled

Reviewer Checklist

Before merging this PR, make sure the following tasks are complete:

• I made sure there are no active labels that block merge
• I followed the testing instructions
• I made sure the CI checks pass
• I reviewed the file changes on GitHub
• I checked that all requirements of the ticket (if any) are fulfilled