PVector angleBetween returns 0 when x and y of either parameter are both 0

I found an existing report describing similar behavior with 3D PVectors (https://github.com/processing/processing/issues/2045), but it appears the same problem affects 2D PVectors as well.

When either the start or end PVector is (0,0) the output of angleBetween() is always 0.

I'm not particularly experienced with Processing, so it's entirely possible that I'm misunderstanding something or using the API incorrectly. I tend to pick it up every few months for small projects and then promptly forget most of what I learned.

That said, I've spent some time testing this behavior and looking into the implementation, and based on what I found, I would not expect the angle to be 0 in the cases I tested.

Edit: I forgot to add, I'm using processing 4.5.2

Parti dal punto di ingresso PVector.angleBetween() e confronta il comportamento 2D con la segnalazione 3D correlata nell’issue #2045. Chiarisci il risultato previsto quando uno dei due vettori è (0,0), quindi verifica il comportamento corretto con una copertura di regressione per questi casi.