Fix mismatch w/ ext-inter/warped-motion/motion-var

Fixes a mismatch issue with ext-inter+motion-var+warped-motion
due to unset num_proj_ref values.

BUG=aomedia:311

Change-Id: I042551f6c53e8cc005f2133704a03b243c98c12a

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 6cd9e30..b9516be 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -8570,6 +8570,9 @@
 #if CONFIG_WARPED_MOTION
   aom_clear_system_state();
   mbmi->num_proj_ref[0] = findSamples(cm, xd, mi_row, mi_col, pts, pts_inref);
+#if CONFIG_EXT_INTER
+  best_bmc_mbmi.num_proj_ref[0] = mbmi->num_proj_ref[0];
+#endif  // CONFIG_EXT_INTER
 #endif  // CONFIG_WARPED_MOTION
 #if CONFIG_MOTION_VAR || CONFIG_WARPED_MOTION
   rate2_nocoeff = rd_stats->rate;