[Fixes #12261] Current user is assigned as owner on geoapp update

[mattiagiupponi]

ref #12261

Checklist

Reviewing is a process done by project maintainers, mostly on a volunteer basis. We try to keep the overhead as small as possible and appreciate if you help us to do so by completing the following items. Feel free to ask in a comment if you have troubles with any of them.

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• [x] Confirm you have read the contribution guidelines
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• [x] There is a ticket in https://github.com/GeoNode/geonode/issues describing the issue/improvement/feature (a notable exemption is, changes not visible to end-users)
• [x] The issue connected to the PR must have Labels and Milestone assigned
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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 64.14%. Comparing base (33ea4b9) to head (eb0345d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #12262 +/- ## ========================================== + Coverage 64.13% 64.14% +0.01% ========================================== Files 872 872 Lines 52319 52333 +14 Branches 6480 6479 -1 ========================================== + Hits 33553 33568 +15 Misses 17275 17275 + Partials 1491 1490 -1 ```