Views Filter Harmonizer | drupal.org
Normally, when a Views field has been assigned both an exposed filter and a contextual filter, then both filters get applied to the View’s results set — always. This is not configurable behaviour. It’s hard-coded.
This small module allows you to have a contextual filter argument apply only when there is no corresponding regular (exposed) filter value present.
This is most common on initial page load. After that the contextual filters will silently retreat and let the exposed filter values as selected by the visitor do their thing without interfering.