Steps to reproduce:
1) Navigate to Configuration->hosts->graphs. (or graph prototype)
2) Press Create graph.
3) Add name and Item.
4) Press Add.

Result:
Item removed/deleted.
Error message that - "Missing items for graph".
Runtime error appears -

Undefined index: pattern [zabbix.php:22 -> require_once() -> ZBase->run() -> ZBase->processRequest() -> ZBase->processResponseFinal() -> CView->getOutput() -> include() -> CConfigFile->{closure}() in app/views/popup.generic.php:564]

Expected:
No error. Graph added.