tests: fakesink: fix string leak in unit test
tests: fakesink: fix string leak in unit test

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