Incorrect host name in graph prototype widget

Steps to reproduce:

1. Create host "host-1" with item "i1".
2. Create host "host-2" with discovery rule "dr" with item prototype "ip1".
3. Create graph prototype "graph" for discovery rule "dr" and add item"i1" first, then add item prototype "ip1".
4. Create dashboard widget "Graph prototype".
5. Type "graph" in Graph prototype multiselect.
6. Observed: incorrect "host-1" is shown as graph prototype host.
7. Click "Select" button for "Graph prototype" field.
8. Select "host-2" in filter and click on "graph".
9. Observed: incorrect "host-1" is shown as graph prototype host.
10. Save widget.
11. Observed: incorrect "host-1" is shown as widget header.

Expected:
In all cases "host-2" should be shown as graph prototype host.