Fix compiler warnings

Change-Id: I2a97f08cc3c7808ce5be39e910cc5147ecf03a1d
diff --git a/vp8/encoder/firstpass.c b/vp8/encoder/firstpass.c
index f0ddbf2..ced2d7c 100644
--- a/vp8/encoder/firstpass.c
+++ b/vp8/encoder/firstpass.c
@@ -1232,6 +1232,8 @@
 
     start_pos = cpi->stats_in;
 
+    vpx_memset(&next_frame, 0, sizeof(next_frame)); // assure clean
+
     // Preload the stats for the next frame.
     mod_frame_err = calculate_modified_err(cpi, this_frame);
 
@@ -2038,6 +2040,8 @@
     double kf_group_coded_err = 0.0;
     double two_pass_min_rate = (double)(cpi->oxcf.target_bandwidth * cpi->oxcf.two_pass_vbrmin_section / 100);
 
+    vpx_memset(&next_frame, 0, sizeof(next_frame)); // assure clean
+
     vp8_clear_system_state();  //__asm emms;
     start_position = cpi->stats_in;