Fix high bit-depth distortion computation

Resolve the segmentation fault issue in nightly run unit test
AV1/AltRefForcedKeyTestLarge.Frame1IsKey/0

Change-Id: Ib27ac0d41767f39114905b7edb6c220bf62214a1

av1/encoder/rdopt.c

@@ -1497,8 +1497,13 @@ static void dist_block(const AV1_COMP *cpi, MACROBLOCK *x, int plane,
 #endif  // CONFIG_DAALA_DIST
       } else {
 #if CONFIG_AOM_HIGHBITDEPTH
+        uint8_t *recon;
         DECLARE_ALIGNED(16, uint16_t, recon16[MAX_TX_SQUARE]);
-        uint8_t *recon = CONVERT_TO_BYTEPTR(recon16);
+
+        if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH)
+          recon = CONVERT_TO_BYTEPTR(recon16);
+        else
+          recon = (uint8_t *)recon16;
 #else
         DECLARE_ALIGNED(16, uint8_t, recon[MAX_TX_SQUARE]);
 #endif  // CONFIG_AOM_HIGHBITDEPTH