Fix use of unintialized variable introduced in r20411.

Originally committed as revision 24005 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/vorbis_dec.c

@@ -576,7 +576,8 @@ static int vorbis_parse_setup_hdr_floors(vorbis_context *vc)
                 int idx;
                 uint_fast8_t book_idx;
                 for (idx = 0; idx < floor_setup->data.t0.num_books; ++idx) {
-                    GET_VALIDATED_INDEX(floor_setup->data.t0.book_list[idx], 8, vc->codebook_count)
+                    GET_VALIDATED_INDEX(book_idx, 8, vc->codebook_count)
+                    floor_setup->data.t0.book_list[idx] = book_idx;
                     if (vc->codebooks[book_idx].dimensions > max_codebook_dim)
                         max_codebook_dim = vc->codebooks[book_idx].dimensions;
                 }