gstpad: Fix PROBE_NO_DATA macro
gstpad: Fix PROBE_NO_DATA macro

The problem was that the macro was always used with 'ret' as the defaultval
argument.

This would result in the macro eventually expanding to
    if (G_UNLIKELY (ret != ret && ret != GST_FLOW_OK))

... ret != ret will always fail, and therefore we'd never call the
following line.

Instead of that, store the previous value locally for comparision

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