MDEV-32965: Assertion `thd->active_stmt_arena_to_use()->...

MDEV-32965:  Assertion `thd->active_stmt_arena_to_use()-> is_stmt_prepare_or_first_sp_execute() || thd->active_stmt_arena_to_use()-> is_conventional() || thd->active_stmt_arena_to_use()->state == Query_arena::STMT_SP_QUERY_ARGUMENTS' failed

This patch fixes too strong condition in assert at the method
  Item_func_group_concat::fix_fields
that is true in case of a stored routine and obviously broken
for a prepared statement.

mysql-test/main/ps.result

@@ -5805,5 +5805,15 @@ END;
 $
 ERROR 42000: EXECUTE..USING does not support subqueries or stored functions
 #
+#  MDEV-32965: Assertion `thd->active_stmt_arena_to_use()-> is_stmt_prepare_or_first_sp_execute() || thd->active_stmt_arena_to_use()-> is_conventional() || thd->active_stmt_arena_to_use()->state == Query_arena::STMT_SP_QUERY_ARGUMENTS' failed
+#
+CREATE TABLE t (f VARCHAR(8)) CHARACTER SET utf8;
+INSERT INTO t VALUES ('foo'),('bar');
+EXECUTE IMMEDIATE 'SELECT GROUP_CONCAT(@x) FROM t GROUP BY @x := f';
+GROUP_CONCAT(@x)
+0
+0
+DROP TABLE t;
+#
 # End of 10.4 tests
 #

mysql-test/main/ps.test

@@ -5231,6 +5231,18 @@ $
 
 delimiter ;$
 
+--echo #
+--echo #  MDEV-32965: Assertion `thd->active_stmt_arena_to_use()-> is_stmt_prepare_or_first_sp_execute() || thd->active_stmt_arena_to_use()-> is_conventional() || thd->active_stmt_arena_to_use()->state == Query_arena::STMT_SP_QUERY_ARGUMENTS' failed
+--echo #
+CREATE TABLE t (f VARCHAR(8)) CHARACTER SET utf8;
+
+INSERT INTO t VALUES ('foo'),('bar');
+EXECUTE IMMEDIATE 'SELECT GROUP_CONCAT(@x) FROM t GROUP BY @x := f';
+
+# Cleanup
+
+DROP TABLE t;
+
 --echo #
 --echo # End of 10.4 tests
 --echo #

sql/item_sum.cc

@@ -4099,7 +4099,7 @@ Item_func_group_concat::fix_fields(THD *thd, Item **ref)
     String *new_separator;
 
     DBUG_ASSERT(thd->active_stmt_arena_to_use()->
-                  is_stmt_prepare_or_first_sp_execute() ||
+                  is_stmt_prepare_or_first_stmt_execute() ||
                 thd->active_stmt_arena_to_use()->
                   is_conventional() ||
                 thd->active_stmt_arena_to_use()->state ==