Flamescope initial click-drag fails

If I try to select a region in the flamescope with click-dragging, I can't do it on the initial click as it won't let me drag the region. I have to click a second time and then I can proceed with dragging.

To reproduce, in the flamescope view:

1. Click "Clear Selection"
2. Initiate a click-drag (you should see that you can't drag the region)
3. Try another click-drag (this time it'll work)

Also see:
- https://github.com/elastic/devfiler/pull/73#issuecomment-3914227517