search/filter string is invisibly applied when reopening dropdown

When the user searches in the dropdown, and then closes and reopens it, the search still applies, but the search text is not displayed. This can be confusing.

#### How to reproduce
- Get happychat client up and running
- Click `I need help with` dropdown.
- Type a character or two to filter the list => note the filtered list of items. Or type something that filters the list so it's empty!
- Close the dropdown by clicking the little arrow on the right.
- Reopen the dropdown => the filter is still applied, but the search text is gone - UI is inconsistent!

Start by running the happychat client and reproducing the dropdown behavior described in the issue. Trace the dropdown's search and filtering entry point to find why the filter remains while its text is hidden after reopening. Done means the reopened dropdown displays the active search text and its filtered list remains consistent.

Written by the indexing model from the issue text.