Fix a typo regarding checking whether HA_VAR_LENGTH_KEY is

set. This has always worked because when flag is !=0 then
HA_VAR_LENGTH_KEY is always set. Therefore, a test case cannot
reveal a faulty behavior.

Fix for bug#23074: typo in myisam/sort.c


myisam/sort.c:
  fix typo. Nevertheless, it has worked as expected
  because when a bit in flag is set HA_VAR_LENGTH_KEY has
  been always set too. Actually, no problem exposed through
  DDL.

myisam/sort.c

@@ -324,7 +324,7 @@ pthread_handler_decl(thr_find_all_keys,arg)
   if (info->sort_info->got_error)
     goto err;
 
-  if (info->keyinfo->flag && HA_VAR_LENGTH_KEY)
+  if (info->keyinfo->flag & HA_VAR_LENGTH_KEY)
   {
     info->write_keys=write_keys_varlen;
     info->read_to_buffer=read_to_buffer_varlen;
@@ -513,7 +513,7 @@ int thr_write_keys(MI_SORT_PARAM *sort_param)
   {
     if (got_error)
       continue;
-    if (sinfo->keyinfo->flag && HA_VAR_LENGTH_KEY)
+    if (sinfo->keyinfo->flag & HA_VAR_LENGTH_KEY)
     {
       sinfo->write_keys=write_keys_varlen;
       sinfo->read_to_buffer=read_to_buffer_varlen;