ffmpeg: remove unneeded ost->picref check.

If there ost->picref is NULL, it will likely crash anyway a few lines
below by dereferencing it in order to access video attribute.

ffmpeg.c

@@ -2141,10 +2141,8 @@ static int transcode_video(InputStream *ist, AVPacket *pkt, int *got_output, int
             }
             filtered_frame = ist->filtered_frame;
             *filtered_frame= *decoded_frame; //for me_threshold
-            if (ost->picref) {
-                avfilter_fill_frame_from_video_buffer_ref(filtered_frame, ost->picref);
-                filtered_frame->pts = av_rescale_q(ost->picref->pts, ist_pts_tb, AV_TIME_BASE_Q);
-            }
+            avfilter_fill_frame_from_video_buffer_ref(filtered_frame, ost->picref);
+            filtered_frame->pts = av_rescale_q(ost->picref->pts, ist_pts_tb, AV_TIME_BASE_Q);
             if (ost->picref->video && !ost->frame_aspect_ratio)
                 ost->st->codec->sample_aspect_ratio = ost->picref->video->sample_aspect_ratio;
             do_video_out(output_files[ost->file_index].ctx, ost, ist, filtered_frame);