fix(heroicons): return early if file not found

[kevinschweikert]

While working on a fix for aptinio/canonical_tailwind#11 i discovered that canonical_tailwind asks the each plugin for each class if it is managed by it. So the heroicons plugin also received a request for "3px" for an arbitrary class like "p-[3px]" and the call to fs.readFileSync errored with path must be a string or a file descriptor. This fix just introduces an early return when the path is not known.

[SteffenDE]

Can that be fixed in canonical_tailwind instead? It seems wrong to pass a class that doesn't match to a plugin that explicitly uses matchComponents to only look for hero-; I'm not against merging this change, but it feels like handling it in the wrong place, so if it can be fixed there, that's what I would prefer.

[aptinio]

Fixed upstream in tailwindlabs/tailwindcss#20052, released in 4.3.1.

[SteffenDE]

Thanks for checking!