Fix simple product editing

[dominik-zeglen]

Resolves #3452
Resolves #3437

Pull Request Checklist

1. Privileged views and APIs are guarded by proper permission checks.
2. All visible strings are translated with proper context.
3. All data-formatting is locale-aware (dates, numbers, and so on).
4. Database queries are optimized and the number of queries is constant.
5. Database migration files are up to date.
6. The changes are tested.
7. The code is documented (docstrings, project documentation).
8. GraphQL schema and type definitions are up to date.
9. Changes are mentioned in the changelog.

[codecov]

Codecov Report

Merging #3474 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3474   +/-   ##
=======================================
  Coverage   89.75%   89.75%           
=======================================
  Files         237      237           
  Lines       12943    12943           
  Branches     1312     1312           
=======================================
  Hits        11617    11617           
  Misses        922      922           
  Partials      404      404

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@599c46d). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #3474   +/-   ##
=========================================
  Coverage          ?   89.75%           
=========================================
  Files             ?      237           
  Lines             ?    12949           
  Branches          ?     1313           
=========================================
  Hits              ?    11622           
  Misses            ?      922           
  Partials          ?      405

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 599c46d...aaa56dc. Read the comment docs.