A collection a saved file references by its asset key (the form library
collections keep) instead of a guid resolved to nothing, so every
explicitVariableModes entry was dropped silently and bound layers rendered
in the collection's default mode (#267). The .fig import now resolves such
references against the file's own nodes (the collection node carries the
same key) for mode entries and the variables' collection link, and reports
modes of collections it can't resolve.