MDEV-15738 Server crashes in my_strcasecmp_utf8 on query from I_S with UNION executed as PS

Problem was the Item_field::Item_field(THD*, Field*) had old code
that put a null pointer in orig_field_names. Now, when we have
proper re-prepare if table definition changes, this is not needed
anymore.

1 files changed, 3 insertions, 6 deletions

diff --git a/sql/item.cc b/sql/item.cc
index b32967e8944..41944d24e8c 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -3077,12 +3077,9 @@ Item_field::Item_field(THD *thd, Field *f)
    have_privileges(0), any_privileges(0)
 {
   set_field(f);
-  /*
-    field_name and table_name should not point to garbage
-    if this item is to be reused
-  */
-  orig_table_name= "";
-  orig_field_name= null_clex_str;
+
+  orig_table_name= table_name;
+  orig_field_name= field_name;
   with_field= 1;
 }