patch 8.0.0220: completion of highlight names misses a few values

Problem:    Completion for :match does not show "none" and other missing
            highlight names.
Solution:   Skip over cleared entries before checking the index to be at the
            end.
diff --git a/src/syntax.c b/src/syntax.c
index d5c2e77..dbadb70 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -9956,6 +9956,13 @@
     char_u *
 get_highlight_name(expand_T *xp UNUSED, int idx)
 {
+    if (idx < 0)
+	return NULL;
+    /* Items are never removed from the table, skip the ones that were cleared.
+     */
+    while (idx < highlight_ga.ga_len && HL_TABLE()[idx].sg_cleared)
+	++idx;
+
 #ifdef FEAT_CMDL_COMPL
     if (idx == highlight_ga.ga_len && include_none != 0)
 	return (char_u *)"none";
@@ -9968,12 +9975,6 @@
 							 && include_link != 0)
 	return (char_u *)"clear";
 #endif
-    if (idx < 0)
-	return NULL;
-    /* Items are never removed from the table, skip the ones that were cleared.
-     */
-    while (idx < highlight_ga.ga_len && HL_TABLE()[idx].sg_cleared)
-	++idx;
     if (idx >= highlight_ga.ga_len)
 	return NULL;
     return HL_TABLE()[idx].sg_name;