Created attachment 734437 [details]
example

Description of problem:
The new charts works without any issues on the Inventory -> Summary tab -> group metric portlet for resources, but for some groups empty popup window is showed or exception is thrown for some autogroups.



Version-Release number of selected component (if applicable):
4.7.0-SNAPSHOT

How reproducible:
always

Steps to Reproduce:
1. inventory some platform
2. create new compatible group with 1 resource of type JBossAS7 Standalone Server (RHQ server)
3. click on newly created group
4. Click on "Maximum request time" link within the "Group: Metric" portlet (this metric should be added by default)

Actual results:
empty window is shown

Expected results:
graph with data should be rendered as it works on the summary tab for the resrource itself (not for group with this resource)

Additional info:

The strange thing is that for some groups, it works well. For instance the autogroup of CPUs shows the proper graphs, but if one creates a common compatible group with some resources of type CPU. Then empty window is shown when clicking on that link on group metric portlet for summary tab for the comp. group. 

For autogroup "JBossAS7 Standalone Servers" it throws an exception (see the attachment)