MDEV-9576 syntax error on view with nullif and count

don't transform Item_func_nullif if it's context_analysis_only

mysql-test/r/null.result

@@ -1524,6 +1524,13 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select nullif(<cache>(avg(`test`.`t1`.`a`)),0) AS `NULLIF(AVG(a),0)` from `test`.`t1`
 DROP TABLE t1;
+create table t1 (col1 varchar(50));
+create view v1 AS select nullif(count(distinct col1),0) from t1;
+show create view v1;
+View	Create View	character_set_client	collation_connection
+v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select nullif(count(distinct `t1`.`col1`),0) AS `nullif(count(distinct col1),0)` from `t1`	latin1	latin1_swedish_ci
+drop view v1;
+drop table t1;
 #
 # End of 10.1 tests
 #

mysql-test/t/null.test

@@ -949,6 +949,15 @@ EXPLAIN EXTENDED SELECT NULLIF(AVG(a),0) FROM t1;
 
 DROP TABLE t1;
 
+#
+# MDEV-9576 syntax error on view with nullif and count
+#
+create table t1 (col1 varchar(50));
+create view v1 AS select nullif(count(distinct col1),0) from t1;
+show create view v1;
+drop view v1;
+drop table t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item_cmpfunc.cc

@@ -2584,7 +2584,7 @@ Item_func_nullif::fix_length_and_dec()
     args[0] and args[2] should still point to the same original l_expr.
   */
   DBUG_ASSERT(args[0] == args[2] || thd->stmt_arena->is_stmt_execute());
-  if (args[0]->type() == SUM_FUNC_ITEM)
+  if (args[0]->type() == SUM_FUNC_ITEM && !thd->lex->context_analysis_only)
   {
     /*
       NULLIF(l_expr, r_expr)
@@ -2757,7 +2757,7 @@ void Item_func_nullif::print(String *str, enum_query_type query_type)
       Note, the EXPLAIN EXTENDED and EXPLAIN FORMAT=JSON routines
       do pass QT_ITEM_FUNC_NULLIF_TO_CASE to print().
     */
-    DBUG_ASSERT(args[0] == args[2]);
+    DBUG_ASSERT(args[0] == args[2] || current_thd->lex->context_analysis_only);
     str->append(func_name());
     str->append('(');
     args[2]->print(str, query_type);