Results are incorrect when using "is not" filter in the Activity Streams gadget

Issue Summary

This is reproducible on Data Center: n/a

Results are incorrect when using "is not" filter in the Activity Streams gadget.

Steps to Reproduce

1. Create a dashboard.
2. Add an Activity Stream gadget in the dashboard.
3. Add  is not filter e.g. Account ID is not for any user.
4. Save.

Expected Results

The result should include all the data that matches the logic of the filter. 

Actual Results

The results do not show the data at all. 

Workaround

If possible, depending on the number of users, you can use the 'is' filter to add all the objects , except for the one object you want to exclude.