1352: Analyze Volume doesn't re-enable [#7501]

[M3wThr33]

I guess Analyze volume doesn't work on video files, so it grays itself out on the context menu. However if you select one in a group of files and leave just mp3s, it doesn't re-enable it.

Reproduction:
1: Ctrl+A on a folder with a bunch of mp3s and 2 movs and 2 mp4s
2: Right-click and see it is disabled.
3: Ctrl+click on the movie files and only mp3 files are left selected and see it is STILL disabled.

[Lowlander]

I'm able to reproduce. Added as: http://www.ventismedia.com/mantis/view.php?id=7501