Fix build on FFmpeg version < 7

Author: ddennedy

src/modules/avformat/filter_avfilter.c

@@ -1061,7 +1061,9 @@ static void filter_close(mlt_filter filter)
         avfilter_graph_free(&pdata->avfilter_graph);
         av_frame_free(&pdata->avinframe);
         av_frame_free(&pdata->avoutframe);
+#if HAVE_FFMPEG_CH_LAYOUT
         av_channel_layout_uninit(&pdata->ch_layout);
+#endif
         free(pdata);
     }
     filter->child = NULL;

src/modules/avformat/link_avfilter.c

@@ -1169,7 +1169,9 @@ static void link_close(mlt_link self)
             avfilter_graph_free(&pdata->avfilter_graph);
             av_frame_free(&pdata->avinframe);
             av_frame_free(&pdata->avoutframe);
+#if HAVE_FFMPEG_CH_LAYOUT
             av_channel_layout_uninit(&pdata->ch_layout);
+#endif
             free(pdata);
         }
         self->close = NULL;