Feeds event with relation to unknown to the widget

[maheichyk]

Events that relate to unknown parent are not added to the timeline and therefore are not passed to the widget. Room timeline is used in StopGapWidget to check if event is before the marker in order to pass it.

This PR suggests to ignore marker timeline logic for these events.

Checklist

• [x] Tests written for new code (and old code if feasible)
• [x] Linter and other CI checks pass
• [x] Sign-off given on the changes (see CONTRIBUTING.md)

Type: defect