Change artist selection, erases value

[dmcle...@gmail.com]

When changing the artist selection (e.g., artist, album-artist, bitrate, comment...., the value field is erased and set to blank.  The UI should preserve the value of the condition.  For example, I selected album-artist equals Led Zeppelin.  I change album-artist to artist, and the value of Led Zeppelin is erased.  I had to redo my entire smart-playlist because I selected the wrong artist value.

Thank you

[Simon Weber]

Ah, yeah, I've been bit by this as well. It's handled by a 3rd party library so I'm not familiar with exactly what it's doing to cause this, but I'll check if it's straightforward to fix.

I opened #179 to track this.