Make subsequence only works if project panel window has focus

Reproduction steps:
1. Click on the sequence window so it has focus

2. On a video track, highlight some clips and right click and select "make subequence"

3. The source panel opens and no subsequence is created in the project window.

Workaround:

1. Click on the sequence window so it has focus

2. On a video track, highlight some clips.
3. Click back on the project panel so it has focus (with the highlight around it)

4. Go back to the highlighted sequence (do not left click on anything to give the window focus), right click on the highlighted clips and select "make subseqence"

5. The subseqence then shows up in the Project panel with the "sub" text in the naming.

and right click and select "make subequence"