Function phase_asset_files 

pub fn phase_asset_files(
    parsed: &[ParsedFile],
    available: Option<&BTreeSet<String>>,
    errors: &mut ErrorSink,
)

bynk.asset.missing_file for each asset whose (otherwise valid) path names no file in available — the project’s assets/ folder as the caller read it (bynk_project::assets). None skips the check: nothing on disk was consulted (an in-memory check). A build passes Some, an empty set when it had no filesystem, so it never invents a URL for a file nobody read.

A path that already fails path_errors is not also reported missing.