If it were valueless you would impair it down to zero and you can’t own an asset that is negative so zero is rock bottom
However if, for some reason, there is a liability connected with the investment in the associate (although I can’t imagine this happening so it’s pure conjecture!) the it would be the case that the liability arising from the investment would be shown
But, even then, it surely wouldn’t be shown as a negative asset Investment in Associate
Why do you ask – it has never appeared as an issue at F7 nor, to my knowledge, at P2