x264enc: when setting fallback decoder latency, set valid min_latency
x264enc: when setting fallback decoder latency, set valid min_latency

Min. latency needs to be a valid time, so pass 0 as default
value in the fallback case where we can't determine any latency,
and avoid nasty criticals at runtime.

GrokImageCompression/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,jar1karp/gst-plugins-ugly,Distrotech/gst-plugins-ugly,krieger-od/gst-plugins-ugly,krieger-od/gst-plugins-ugly,sebras/gst-plugins-ugly,surround-io/gst-plugins-ugly,Lachann/gst-plugins-ugly,GStreamer/gst-plugins-ugly,collects/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,collects/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,krieger-od/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,krieger-od/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,StreamUtils/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,Kurento/gst-plugins-ugly,surround-io/gst-plugins-ugly,Lachann/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,collects/gst-plugins-ugly,Distrotech/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,Lachann/gst-plugins-ugly,Distrotech/gst-plugins-ugly,cablelabs/gst-plugins-ugly,cablelabs/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,jar1karp/gst-plugins-ugly,cablelabs/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,GStreamer/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,sebras/gst-plugins-ugly,GStreamer/gst-plugins-ugly,Kurento/gst-plugins-ugly,jar1karp/gst-plugins-ugly,Distrotech/gst-plugins-ugly,sebras/gst-plugins-ugly,surround-io/gst-plugins-ugly,Kurento/gst-plugins-ugly,collects/gst-plugins-ugly,Distrotech/gst-plugins-ugly