CanvasVisibility#testVisibility return value isn't strictly boolean #8202

Originally reported by Wasp#2005 https://discord.com/channels/170995199584108546/956306859491471420/1019723643724513312

ALL MODULES DISABLED? true
OS, Hosting, Browser (if applicable): Windows, NodeJS, Chrome
Short Description of bug: CanvasVisibility#testVisibility returns void if test fails, which could result in unintended behavior for downstream modules
Simple steps to reproduce the bug:

1. Create a token and hide it on the GM side
2. Log in as a player with visibility on the scene
3. Run canvas.effects.visibility.testVisibility(canvas.tokens.placeables[0].center, { object: canvas.tokens.placeables[0] }); in the console
4. It returns undefined instead of false

Screenshots and/or console errors: