Trying to duplicate Graph Template in Templates menu but got 500 Internal Server Error.
Its seems that the problem in type casting for php > 5 versions.

To fix:

File 'lib/api_graph.php', function 'api_duplicate_graph', line 478

replace from:
$save['hash'] = get_hash_data_query('', 'data_query_graph');
to:
$save['hash'] = get_hash_data_query(0, 'data_query_graph');