category search results list contains categories that have been previously deleted

[ecamuto]

Bug Description
when I search for category (i.e. I'm moving an event to another category) and I type a category name, I get in the result set all the occurrences of that category even if it has been removed (once or many times).
As shown here:

To Reproduce
Steps to reproduce the behavior:

1. Go to a conference page
2. Click on "Event action" and then "Move"
3. "Select a category" will appear
4. Type a category that has been deleted from the system, once or more times
5. In the results list you will get a row the category for every time it has been created (and deleted)

Expected behavior
Category search results should not include categories that have been removed by the system