Fix of the minimum quantity of consumable credits

[Lainow]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !43309
• Here is a brief description of what this PR does
  In the “Credit Voucher” tab, it was no longer possible to add one manually due to a JavaScript error; furthermore, the minimum quantity was always 0 instead of 1.

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