encoder/shine: fix segfault workaround

Initializing and closing the Shine library without
writing any data results in a segmentation fault.
The current workaround writes zeroes if there was
no actual data.
input/despotify: change name to "despotify"

The name "spt" didn't make much sense for this plugin.
Merge branch 'shine' of git://github.com/ekroth/mpd