[17b8 bug report] a couple of bugs

Hello,

This is my first bug report, and I believe this is the correct forum to post it. If it is not the right place, I will appreciate if you could advise me.

1. Speed Editor source navigation in Edit
When an empty timeline is created in Edit page, jog wheel on Speed Editor does not work in source window.
Way to reproduce:

* Drag media to the "Preview" window.
* Create new timeline.
* Source/Timeline preview switching works when pressing buttons on SE (changes highlighted window), but navigation with the jog wheel does not.
* Press "In" button, press "Play", after several seconds stop and press "Out".
* Press "Append". Selected clip is appended to the empty timeline.
* Now navigation in Source window works as expected. Deleting the clip from the timeline does not affect navigation in "Source"

2. Video preview freezes in Fairlight
When playing the video in Faiflight page, the video preview randomly freezes. Sometimes it restarts after several seconds, sometimes freezes for good until playback is restarted. Video frames in the film strip at the bottom of the window are rendered without hiccups.

2. Fairlight will focus on real-time audio playback. If your machine can't handle real time playback of the video portion, this is what happens.

From the Edit page, you can try Caching the problem segments.

2. Fairlight will focus on real-time audio playback. If your machine can't handle real time playback of the video portion, this is what happens.

12 lightly loaded physical cores, 96GB of ram, RTX 2080 should be sufficient. In DR16 playback works fine.

From the Edit page, you can try Caching the problem segments.

It's not a problem with caching. It's navigation not working only when a new empty is created, even when it works fine with other timelines.