Fix DRY_RUN_COSTCOEFFS rate estimate

Change-Id: I050e8a8ffef5c45d9803989c512432c91b8c4dca
diff --git a/av1/encoder/partition_search.c b/av1/encoder/partition_search.c
index 861c4fa..c94de6f 100644
--- a/av1/encoder/partition_search.c
+++ b/av1/encoder/partition_search.c
@@ -418,7 +418,7 @@
                                    PALETTE_MAP, tile_data->allow_update_cdf,
                                    td->counts);
           } else if (dry_run == DRY_RUN_COSTCOEFFS) {
-            rate +=
+            *rate +=
                 av1_cost_color_map(x, plane, bsize, mbmi->tx_size, PALETTE_MAP);
           }
         }