lavfi/graphdump: fix output for unknown layouts.

libavfilter/graphdump.c

@@ -45,7 +45,7 @@ static int print_link_prop(AVBPrint *buf, AVFilterLink *link)
 
         case AVMEDIA_TYPE_AUDIO:
             av_get_channel_layout_string(layout, sizeof(layout),
-                                         -1, link->channel_layout);
+                                         link->channels, link->channel_layout);
             format = av_x_if_null(av_get_sample_fmt_name(link->format), "?");
             av_bprintf(buf, "[%dHz %s:%s]",
                        (int)link->sample_rate, format, layout);