Reduce risk of overflowing in mono downsampling
Not observed yet (except when caused by a different bug), but "just in case"
diff --git a/celt/celt_decoder.c b/celt/celt_decoder.c
index fd744a2..6f7b34d 100644
--- a/celt/celt_decoder.c
+++ b/celt/celt_decoder.c
@@ -333,7 +333,7 @@
denormalise_bands(mode, X+N, freq2, oldBandE+nbEBands, start, effEnd, M,
downsample, silence);
for (i=0;i<N;i++)
- freq[i] = HALF32(ADD32(freq[i],freq2[i]));
+ freq[i] = ADD32(HALF32(freq[i]), HALF32(freq2[i]));
for (b=0;b<B;b++)
clt_mdct_backward(&mode->mdct, &freq[b], out_syn[0]+NB*b, mode->window, overlap, shift, B, arch);
} else {
