avfilter/avfiltergraph: Remove NULL checks after dereferences

Fixes: CID1398579 Dereference before null check
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/avfiltergraph.c

@@ -1360,8 +1360,8 @@ int avfilter_graph_request_oldest(AVFilterGraph *graph)
         if (r != AVERROR_EOF)
             break;
         av_log(oldest->dst, AV_LOG_DEBUG, "EOF on sink link %s:%s.\n",
-               oldest->dst ? oldest->dst->name : "unknown",
-               oldest->dstpad ? oldest->dstpad->name : "unknown");
+               oldest->dst->name,
+               oldest->dstpad->name);
         /* EOF: remove the link from the heap */
         if (oldest->age_index < --graph->sink_links_count)
             heap_bubble_down(graph, graph->sink_links[graph->sink_links_count],