fix static combo chart crashes when viz settings are invalid

[alxnddr]

Closes #42282

Description

Fixes some static charts crashed on Stats. The reason is that questions have outdated and invalid graph.dimensions and graph.metrics settings which weren't validated with the fallback to defaults in the static viz.

How to verify

The newly added story can be used for the verification since it contains invalid viz settings:

"visualization_settings": {
  "graph.dimensions": ["__CREATED_AT", "__CATEGORY"],
  "graph.metrics": ["__count"]
}

Checklist

• Tests have been added/updated to cover changes in this PR

[replay-io]

Status	Complete ↗︎
Commit	c82b4e5
Results	⚠️ 3 Flaky ✅ 2505 Passed