There are some control points that set the 'next uri' to an

empty string when the playlist ends. gstreamer 0.10 has a problem
with that. Consider an empty string just to be NULL.

Fixes bug #38

(merged from upstream commit 1dfa850f21b33c565d8def9a08495fbfc42d3850)
Update README.md with the latest state of the gapless bug

in recent gstreamer versions (and: latest works!).

(merged upstream commit d75db7ace144c37e0c7cfd809f293c57246a6439)