patch 9.1.0618: cannot mark deprecated attributes in completion menu

Problem:  cannot mark deprecated attributes in completion menu
Solution: add hl_group to the Dictionary of supported completion fields
          (glepnir)

closes: #15314

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 0267d28..a33d6be 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -359,6 +359,7 @@
 	compl_match_array[i].pum_info = NULL;
 	compl_match_array[i].pum_extra = NULL;
 	compl_match_array[i].pum_kind = NULL;
+	compl_match_array[i].pum_extrahlattr = -1;
     }
 
     // Compute the popup menu starting column