An unlimited use discount code created under certain conditions if seat cost is 0

[dwanjuki]

Describe the bug
When the seats parameter is omitted from the $pmprosm_sponsored_account_levels array and if the sponsored seats are free, checking out for a sponsor level without creating any child accounts creates an unlimited use discount code.

An unlimited use discount code is also created if a parent account is imported from CSV.

To Reproduce
Steps to reproduce the behavior:

1. Setup your $pmprosm_sponsored_account_levels array. Omit seats and set seat_cost to 0
2. Check out for the sponsored level. Do not create any seats at checkout.
3. Check Memberships > Settings > Discount Codes
4. Observe that the discount code created has unlimited uses.

Expected behavior
Number of discount code uses is limited

Isolating the problem (mark completed items with an [x]):

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.

WordPress Environment

WP 6.2 PMPro 2.10.5 PMPro Sponsored Members 0.10.1