Regression, broken in rev 30872 (ZBX-5137)

How to reproduce:
1. open Monitoring -> Graphs and select a "Group A" hosts group in filter.
2. goto to Monitoring -> Screens.
Here you have to have a resource cell type "Graph" from a host which is member only of a "Group B" hosts group.
3. try to click to this graph to open it.
It should open this one graph zoomed to page width. But you will see "No graphs defined." and in the filter above you will see host group "Group A" preselected.