MDEV-12495 Conditional jump depends on uninitialised value for: SELECT NULL UNION geom_expression

mysql-test/r/gis.result

@@ -1630,3 +1630,16 @@ SELECT ASTEXT(p) FROM v1;
 ASTEXT(p)
 POINT(1 1)
 DROP VIEW v1;
+#
+# Start of 10.0 tests
+#
+#
+# MDEV-12495 Conditional jump depends on uninitialised value for: SELECT NULL UNION geom_expression
+#
+SELECT AsText(g) FROM (SELECT NULL AS g UNION SELECT Point(1,1)) AS t1;
+AsText(g)
+NULL
+POINT(1 1)
+#
+# End 10.0 tests
+#

mysql-test/t/gis.test

@@ -1492,3 +1492,16 @@ SELECT ASTEXT(p) FROM v1;
 DROP VIEW v1;
 
 # --echo End of 5.5 tests
+
+--echo #
+--echo # Start of 10.0 tests
+--echo #
+
+--echo #
+--echo # MDEV-12495 Conditional jump depends on uninitialised value for: SELECT NULL UNION geom_expression
+--echo #
+SELECT AsText(g) FROM (SELECT NULL AS g UNION SELECT Point(1,1)) AS t1;
+
+--echo #
+--echo # End 10.0 tests
+--echo #

sql/item.cc

@@ -9464,7 +9464,10 @@ void Item_cache_row::set_null()
 
 
 Item_type_holder::Item_type_holder(THD *thd, Item *item)
-  :Item(thd, item), enum_set_typelib(0), fld_type(get_real_type(item))
+  :Item(thd, item),
+   enum_set_typelib(0),
+   fld_type(get_real_type(item)),
+   geometry_type(Field::GEOM_GEOMETRY)
 {
   DBUG_ASSERT(item->fixed);
   maybe_null= item->maybe_null;