Visitor groups appear in search result for "groups" when capitalizing/uncapitalizing first letter

Description

Steps to reproduce:

1. Create a new visitor group with the name "MyVisitorGroup" and select the check box "Make this visitor group available when setting access rights for pages and files".

2. Go to a page and click Visible to > Manage. In the Access Rights dialog box, click Add Users/Groups, and search for "MyVisitorGroup" using the type "Visitor Groups". It results in one hit as expected.

3. Change the type to "Groups" and make a new search. It results in no hits.

4. Search again using the type "Groups" but change the first letter of the visitor group name to a lower letter "myVisitorGroup" and search again.

Expected result:

The visitor group should not show up.

Actual result:

Visitor group shows up in result.