Trailing parenthesis in search URL is erased sometimes

Created by: rvantonder

On Sourcegraph version: 3.18 and master

A URL containing patternType=regexp for a query like repo:(sourcegraph) works as expected.

When The URL does not contain patterntype=XXX, a trailing parenthesis in the URL is erased. Here is an example of a URL containing the trailing ) (encoded as %29), but when the value is populated in the search bar, the trailing ) briefly appears and is then erased:

https://sourcegraph.com/search?q=repo:%28sourcegraph%29

This seems almost certainly related to https://github.com/sourcegraph/sourcegraph/issues/12506

Customer reported working previously, but broken as of 3.18.