[libvpx] scan-build: Division by zero - measure_square_diff_partial()

libs/libvpx/vp8/encoder/onyx_if.c

@@ -3007,7 +3007,7 @@ static int measure_square_diff_partial(YV12_BUFFER_CONFIG *source,
   // Only return non-zero if we have at least ~1/16 samples for estimate.
   if (num_blocks > (tot_num_blocks >> 4)) {
     assert(num_blocks != 0);
-    return (Total / num_blocks);
+    return num_blocks ? (Total / num_blocks) : 0;
   } else {
     return 0;
   }