Fixed bug with BINARY NULL

Docs/manual.texi:
  ChangeLog
mysql-test/r/binary.result:
  Test of binary NULL
mysql-test/t/binary.test:
  Test of binary NULL

Docs/manual.texi

@@ -46929,6 +46929,8 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.53
 @itemize @bullet
 @item
+Fixed core dump bug when using the @code{BINARY} cast on a @code{NULL} value.
+@item
 Fixed bug in @code{ALTER TABLE} and @code{RENAME TABLE} when running with
 @code{-O lower_case_table_names=1} (typically on windows) when giving the
 table name in uppercase.

mysql-test/r/binary.result

@@ -31,3 +31,7 @@ hello	hello
 a	b
 a	b
 hello	hello
+b
+b
+NULL
+b

mysql-test/t/binary.test

@@ -31,3 +31,13 @@ select * from t1 where a="hello ";
 select * from t1 where b="hello ";
 select * from t1 where b="hello";
 drop table t1;
+
+#
+# Test of binary and NULL
+#
+create table t1 (b char(8));
+insert into t1 values(NULL);
+select b from t1 where binary b like '';
+select b from t1 group by binary b like '';
+select b from t1 having binary b like '';
+drop table t1;

sql/item_strfunc.h

@@ -394,7 +394,12 @@ class Item_func_binary :public Item_str_func
 public:
   Item_func_binary(Item *a) :Item_str_func(a) {}
   const char *func_name() const { return "binary"; }
-  String *val_str(String *a) { return (args[0]->val_str(a)); }
+  String *val_str(String *a)
+  {
+    String *tmp=args[0]->val_str(a);
+    null_value=args[0]->null_value;
+    return tmp;
+   }
   void fix_length_and_dec() { binary=1; max_length=args[0]->max_length; }
   void print(String *str) { print_op(str); }
 };