Fix a build issue for --enable-intern-stats

Change-Id: Iea7c9fa0726dbf9792eea79e6a05eb8a3c718d45

vp9/encoder/vp9_encodeframe.c

diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index 35aa45f..b97fd02 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -1075,7 +1075,7 @@
       THR_D63_PRED /*D63_PRED*/,
       THR_TM /*TM_PRED*/,
     };
-    cpi->mode_chosen_counts[kf_mode_index[mi->mbmi.mode]]++;
+    ++cpi->mode_chosen_counts[kf_mode_index[mbmi->mode]];
 #endif
   } else {
     // Note how often each mode chosen as best