Editing graphs can cause errors due to missing sequence

[netniV]

Describe the bug

2021/07/08 15:50:52 - CMDPHP PHP ERROR NOTICE Backtrace: (
	/graphs.php[116]:graph_edit(), 
	/graphs.php[1650]:item(), 
	/graphs.php[1377]:draw_graph_items_list(), 
	/lib/html.php[1170]:CactiErrorHandler()
)
2021/07/08 15:50:52 - ERROR PHP NOTICE: Undefined index: sequence in file: 
	/usr/share/cacti/lib/html.php on line: 1170

To Reproduce

I believe that this error is generated by saving a graph template.

[TheWitness]

I did not find a CHANGELOG entry for this one.