aacdec: reorder multiuplications to make code safer against too large input values.

Fixes CID700697
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/aacdec.c

@@ -1242,7 +1242,7 @@ static void decode_mid_side_stereo(ChannelElement *cpe, GetBitContext *gb,
         for (idx = 0; idx < cpe->ch[0].ics.num_window_groups * cpe->ch[0].ics.max_sfb; idx++)
             cpe->ms_mask[idx] = get_bits1(gb);
     } else if (ms_present == 2) {
-        memset(cpe->ms_mask, 1, cpe->ch[0].ics.num_window_groups * cpe->ch[0].ics.max_sfb * sizeof(cpe->ms_mask[0]));
+        memset(cpe->ms_mask, 1,  sizeof(cpe->ms_mask[0]) * cpe->ch[0].ics.num_window_groups * cpe->ch[0].ics.max_sfb);
     }
 }