basesink: handle empty buffer list more gracefully
basesink: handle empty buffer list more gracefully

Don't abort, just ignore it. It's like a buffer
without memories.

shelsonjava/gstreamer,krichter722/gstreamer,mparis/gstreamer,mparis/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,centricular/gstreamer,mparis/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,centricular/gstreamer