scripts/vim-patch.sh: include --shortstat with -m

scripts/vim-patch.sh

@@ -598,7 +598,9 @@ list_missing_previous_vimpatches_for_patch() {
   if [[ -z "${missing_list[*]}" ]]; then
     msg_ok 'no missing previous Vim patches'
     set -u
-    return 0
+    return 0
+  fi
+  set -u
 
   local -a missing_unique
   while IFS= read -r line; do