Dark Mode is one of the most publicized features of macOS Mojave. Unfortunately, it has a minor flaw that could make it unusable for some users. Thankfully, there's a new third-party app, NightOwl, that removes this obstacle.
IMPORTANT: security researchers recently found out that since it was recently bought out by another company, NightOwl joins your devices into a botnet for use of market research without your knowledge. More details here.