accumulate_counters_enc_workers: fix invalid free

since:
bd9055e8d Allocate dv_costs when required

Bug: aomedia:3268
Change-Id: Ic15208c6bf4ed79b6c0e8b2edcf3efd2b33ca67f

av1/encoder/ethread.c

diff --git a/av1/encoder/ethread.c b/av1/encoder/ethread.c
index 4cc40fb..7eb63ba 100644
--- a/av1/encoder/ethread.c
+++ b/av1/encoder/ethread.c
@@ -1222,7 +1222,8 @@
       if (cpi->sf.inter_sf.mv_cost_upd_level != INTERNAL_COST_UPD_OFF) {
         aom_free(thread_data->td->mb.mv_costs);
       }
-      if (cpi->sf.intra_sf.dv_cost_upd_level != INTERNAL_COST_UPD_OFF) {
+      if (cpi->sf.intra_sf.dv_cost_upd_level != INTERNAL_COST_UPD_OFF &&
+          av1_need_dv_costs(cpi)) {
         aom_free(thread_data->td->mb.dv_costs);
       }
     }