Hey jitter, thanks for looking into this issue!
I'm concerned about this issue because it is a regression that breaks backwards compatibility with 1.4.3 and is incorrect behavior according to the documentation on .find().
The API documentation for .find() says "The method accepts a selector expression of the same type that we can pass to the $() function." The documentation for the jQuery constructor says "calling the jQuery() method with no arguments returns an empty jQuery set."
With this regression, the behavior of .find() and $() are now inconsistent. Calling .find() should return an empty jQuery set instead of throwing an error.
While it's true that the behavior of .find() in this case was loosely documented, it's likely that there are plugins or other code depending on this behavior. Since this throws an error now it will very likely break other, seemingly unrelated elements on the page. This may prevent people from being able to upgrade.