Resolve an issue between palette and delta-q

Avoid resetting current_q_index.

Change-Id: I76d27605b6a8c0cd6b1032e24ea5ca8561115e5a
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index da14d30..c9c766a 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -10905,7 +10905,7 @@
     uint8_t *const best_palette_color_map =
         x->palette_buffer->best_palette_color_map;
     uint8_t *const color_map = xd->plane[0].color_index_map;
-    MB_MODE_INFO best_mbmi_palette = best_mbmode;
+    MB_MODE_INFO best_mbmi_palette = *mbmi;
 
     mbmi->mode = DC_PRED;
     mbmi->uv_mode = UV_DC_PRED;