Bug#13889741: HANDLE_FATAL_SIGNAL IN _DB_ENTER_ |HANDLE_FATAL_SIGNAL IN STRNLEN

Follow up patch to resolve pb2 failure on windows platform

sql/sql_show.cc

@@ -2784,9 +2784,12 @@ int make_db_list(THD *thd, List<LEX_STRING> *files,
 
   /*
     If we have db lookup vaule we just add it to list and
-    exit from the function
+    exit from the function.
+    We don't do this for database names longer than the maximum
+    path length.
   */
-  if (lookup_field_vals->db_value.str)
+  if (lookup_field_vals->db_value.str && 
+      lookup_field_vals->db_value.length < FN_REFLEN)
   {
     if (is_infoschema_db(lookup_field_vals->db_value.str,
                          lookup_field_vals->db_value.length))