[Fixes #12384] Uploaded thumbnail for 3dtiles resource is not saved

[mattiagiupponi]

ref #12384

Checklist

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 64.18%. Comparing base (514344c) to head (efa7933).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #12385 +/- ## ======================================= Coverage 64.17% 64.18% ======================================= Files 886 886 Lines 53278 53286 +8 Branches 6584 6585 +1 ======================================= + Hits 34191 34201 +10 + Misses 17574 17571 -3 - Partials 1513 1514 +1 ```