Editor freezes up when dragging the scroll bar of the Visual Logger window when a bvlog file isn't loaded

When adjusting the scroll bar in the Visual Logger window, the editor freezes up. There is no callstack provided in the logs. The only way to close the editor at that point is to close it through the Task Manager. This only occurs when a bvlog file is not loaded.

Tested in //UE4/Release-4.25 @ CL 14469661 and the same behavior occurred so not marking as a Regression.

1. Open any project
2. Navigate to Window > Developer Tools > Visual Logger
3. Use scroll wheel on mouse to zoom in on the timeline
4. Click and drag on the white scroll bar to adjust the timeline

RESULT:

Editor freezes with no crash reporter

EXPECTED:

Editor does not freeze when adjusting the timeline