swresample/swresample: Use av_mallocz_array()

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

libswresample/swresample.c

@@ -352,7 +352,7 @@ int swri_realloc_audio(AudioData *a, int count){
     av_assert0(a->bps);
     av_assert0(a->ch_count);
 
-    a->data= av_mallocz(countb*a->ch_count);
+    a->data= av_mallocz_array(countb, a->ch_count);
     if(!a->data)
         return AVERROR(ENOMEM);
     for(i=0; i<a->ch_count; i++){