Add null coalescing for fallback and general settings

[manuelkleinert]

#This PR fixes multiple ErrorException: Warning: Undefined array key errors occurring in SystemSettingsProvider::prepareSettingsForUpdate when saving system settings in Pimcore

Studio.

#Changes in this pull request

• Fixed multiple ErrorException: Warning: Undefined array key errors in SystemSettingsProvider::prepareSettingsForUpdate.
• Added null coalescing operators (??) and default values to all fields in the prepareSettingsForUpdate method to ensure stability when saving system settings.
• Specifically addressed missing keys for:
  • fallback_languages (now defaults to an empty string/array).
  • localized error_pages (now safely handles missing paths).
  • Versioning settings for objects, assets, and documents (days, steps).
  • General settings like domain, required_languages, and debug_admin_translations.
  • Email debug addresses.

#Additional info

This issue occurred when the Pimcore Studio UI sent settings data where certain optional or language-specific fields were missing, causing a 500 Internal Server Error during the
preparation of the update. By adding these safeguards, the backend is now more resilient to incomplete or empty configuration sets, allowing the save process to complete
successfully regardless of the current configuration state.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 26 complexity · 0 duplication

Metric	Results
Complexity	26
Duplication	0

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_{TIP This summary will be updated as you push new changes. Give us feedback}

[martineiber]

@manuelkleinert Thank you for the Contribution. Could you rebase this PR to 2025.4?

[AndrewKMoses]

We have more of these type of errors, but for the function getDocumentSettings and the key error_pages. Could we include the fix for that in this PR?

[martineiber]

@manuelkleinert We would like to include this into 2025.4, Would be nice if you can rebase this PR.

[martineiber]

We have more of these type of errors, but for the function getDocumentSettings and the key error_pages. Could we include the fix for that in this PR?

When the PR is rebased to 2025.4 We can include this. Is it only for error_pages?

[AndrewKMoses]

We have more of these type of errors, but for the function getDocumentSettings and the key error_pages. Could we include the fix for that in this PR?

When the PR is rebased to 2025.4 We can include this. Is it only for error_pages?

Yes

[manuelkleinert]

@manuelkleinert We would like to include this into 2025.4, Would be nice if you can rebase this PR.

I have made the adjustment.