avfilter/af_channelmap: Move ff_add_channel_layout() call to querry_format()

Avoids memleak if querry_formats is not called
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/af_channelmap.c

@@ -275,8 +275,6 @@ static av_cold int channelmap_init(AVFilterContext *ctx)
         return AVERROR(EINVAL);
     }
 
-    ff_add_channel_layout(&s->channel_layouts, s->output_layout);
-
     if (mode == MAP_PAIR_INT_STR || mode == MAP_PAIR_STR_STR) {
         for (i = 0; i < s->nch; i++) {
             s->map[i].out_channel_idx = av_get_channel_layout_channel_index(
@@ -299,6 +297,7 @@ static int channelmap_query_formats(AVFilterContext *ctx)
     if (!layouts)
         return AVERROR(ENOMEM);
 
+    ff_add_channel_layout(&s->channel_layouts, s->output_layout);
     ff_channel_layouts_ref(layouts, &ctx->inputs[0]->out_channel_layouts);
     ff_channel_layouts_ref(s->channel_layouts,       &ctx->outputs[0]->in_channel_layouts);