avfilter/af_astats: redo zero channel handling

Suggested-by: Nicolas George
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/af_astats.c

@@ -222,9 +222,6 @@ static void print_stats(AVFilterContext *ctx)
         av_log(ctx, AV_LOG_INFO, "Peak count: %"PRId64"\n", p->min_count + p->max_count);
     }
 
-    if (!nb_samples || !s->nb_channels)
-        return;
-
     av_log(ctx, AV_LOG_INFO, "Overall\n");
     av_log(ctx, AV_LOG_INFO, "DC offset: %f\n", max_sigma_x / (nb_samples / s->nb_channels));
     av_log(ctx, AV_LOG_INFO, "Min level: %f\n", min);
@@ -243,7 +240,8 @@ static av_cold void uninit(AVFilterContext *ctx)
 {
     AudioStatsContext *s = ctx->priv;
 
-    print_stats(ctx);
+    if (s->nb_channels)
+        print_stats(ctx);
     av_freep(&s->chstats);
 }