[Backport release_3_10] Provide default values for *very* old qgs files with missing attributes

[3liz-bot]

Backport #6113
Authored by: @nworr

[3liz-bot]

All Playwright tests LEGACY

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
340	338	0	2	0	1	12m 23s

Flaky Tests

Flaky Tests 🍂	Retries
Catch GetLegendGraphic requests and timeout on GetLegendGraphic with multi layers	1

Flaky Rate

Flaky Rate	0.29% ( ➖ 0.00%)

Test 📝	Attempts 🎯	Passed ✅	Failed ❌	Flaky Rate 📈
Catch GetLegendGraphic requests and timeout on GetLegendGraphic with multi layers	2	1	1	50.00

_{🎉 No failed tests in this run.}

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All Playwright tests BLEEDING_EDGE

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
340	338	0	2	0	3	12m 27s

Flaky Tests

Flaky Tests 🍂	Retries
should delete	1
Catch GetLegendGraphic requests and timeout on GetLegendGraphic with multi layers	1
Build permalink, reload and apply one	1

Flaky Rate

Flaky Rate	0.87% ( ➖ 0.00%)

Test 📝	Attempts 🎯	Passed ✅	Failed ❌	Flaky Rate 📈
Catch GetLegendGraphic requests and timeout on GetLegendGraphic with multi layers	2	1	1	50.00
Build permalink, reload and apply one	2	1	1	50.00
should delete	3	2	1	33.33
should delete	3	2	1	33.33

_{🎉 No failed tests in this run.}

Github Test Reporter by CTRF 💚