localities parameter - error handling

**Issue:**
If the localities parameter includes an incorrect locality spelling it results in a 500 error. This is not an issue with the notLocalities parameter.

**Example:**
http 200:
https://geocoder.api.gov.bc.ca/addresses.json?addressString=100%20Main%20Street&localities=Penticton

http 500:
https://geocoder.api.gov.bc.ca/addresses.json?addressString=100%20Main%20Street&localities=Pentiton

Start by reproducing the addresses.json request with the misspelled localities value and compare it with the working notLocalities request. Trace how the localities parameter is validated and how the failure becomes an HTTP 500. Done means an incorrect locality spelling is handled without a 500 response while valid localities and notLocalities behavior remain intact.

Written by the indexing model from the issue text.