avfilter/showpalette: fix leak in case of error

Fixes CID1270820
Fixes CID1270818

libavfilter/vf_showpalette.c

@@ -48,8 +48,11 @@ static int query_formats(AVFilterContext *ctx)
     static const enum AVPixelFormat out_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
     AVFilterFormats *in  = ff_make_format_list(in_fmts);
     AVFilterFormats *out = ff_make_format_list(out_fmts);
-    if (!in || !out)
+    if (!in || !out) {
+        av_freep(&in);
+        av_freep(&out);
         return AVERROR(ENOMEM);
+    }
     ff_formats_ref(in,  &ctx->inputs[0]->out_formats);
     ff_formats_ref(out, &ctx->outputs[0]->in_formats);
     return 0;