avcodec/dct: use av_malloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dct.c

@@ -190,7 +190,7 @@ av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
         ff_init_ff_cos_tabs(nbits + 2);
 
         s->costab = ff_cos_tabs[nbits + 2];
-        s->csc2   = av_malloc(n / 2 * sizeof(FFTSample));
+        s->csc2   = av_malloc_array(n / 2, sizeof(FFTSample));
 
         if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
             av_free(s->csc2);