Jakub Adam authored Sep 25, 2014 and Olivier Crête committed Jan 28, 2015

When a nicesink switches to a different component, we should unblock any
pending write waiting in gst_nice_sink_render() for writable_cond being
signalled because if the new transport already is writable, we'll never
get notified about the condition and thus nicesink will wait forever.

That way, either the pending data are immediately sent or the nicesink
blocks again until the transport becomes writable.