decoder_inspect: consume trailing zero bytes

this matches decoder_decode() and fixes decode errors in the analyzer

Change-Id: Ie6bbfa18163c1eb0c9218402d973fe7a862a92c6
diff --git a/av1/av1_dx_iface.c b/av1/av1_dx_iface.c
index 0de272a..38c1dfa 100644
--- a/av1/av1_dx_iface.c
+++ b/av1/av1_dx_iface.c
@@ -582,6 +582,7 @@
                                        void *user_priv) {
   aom_codec_err_t res = AOM_CODEC_OK;
 
+  const uint8_t *const data_end = data + data_sz;
   Av1DecodeReturn *data2 = (Av1DecodeReturn *)user_priv;
 
   if (ctx->frame_workers == NULL) {
@@ -600,6 +601,13 @@
   if (ctx->frame_workers->had_error)
     return update_error_state(ctx, &frame_worker_data->pbi->common.error);
 
+  // Allow extra zero bytes after the frame end
+  while (data < data_end) {
+    const uint8_t marker = data[0];
+    if (marker) break;
+    ++data;
+  }
+
   data2->idx = -1;
   for (int i = 0; i < REF_FRAMES; ++i)
     if (cm->ref_frame_map[i] == cm->cur_frame) data2->idx = i;