avfilter/vf_scale: Set scale2ref ref output timebase

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_scale.c

@@ -428,6 +428,7 @@ static int config_props_ref(AVFilterLink *outlink)
     outlink->w = inlink->w;
     outlink->h = inlink->h;
     outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;
+    outlink->time_base = inlink->time_base;
 
     return 0;
 }