Artless fallback broken

[dextre]

I think the MUSIC_NOTE fallback is currently breaking the script when using the default of kunst.jpg.

When I get error: cover not found online it will write the music_note to /tmp/kunst.png, but sxiv is watching the .jpg, so the display will stay as the last found cover forever, while kunst then keeps writing future (undisplayed) covers as kunst.png. It only works as expected if I start kunst while playing a song with unfindable art, locking itself into using .png from the go, or if you set COVER to png at the top.

I got it working smoothly (while still using jpgs) by just commenting out line 216:
#COVER=/tmp/kunst.png
so it writes the music_note png as kunst.jpg, which sxiv still displays fine, but won't divert the whole thing into only writing pngs.