fix: if config doesn't exist, add minimal one with flowLayout

[tepi]

When Hilla view has no config, make sure to create a minimal config for it, containing the flowLayout value.

Fixes vaadin/flow#20110

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.29%. Comparing base (29cd084) to head (e7122a0).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2793   +/-   ##
=======================================
  Coverage   92.29%   92.29%           
=======================================
  Files          81       81           
  Lines        2673     2675    +2     
  Branches      683      685    +2     
=======================================
+ Hits         2467     2469    +2     
  Misses        156      156           
  Partials       50       50           

Flag	Coverage Δ
unittests	92.29% <100.00%> (+<0.01%)	⬆️

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[sonarcloud]

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 SonarCloud

[vaadin-bot]

This ticket/PR has been released with Hilla 24.5.0.beta6 and is also targeting the upcoming stable 24.5.0 version.