Referencing a Glicol bus before it is defined on its own line causes an unresolved-reference error

Bus names in Glicol (prefixed with ~) must be defined on their own named line before they can be referenced in another chain. Using >> mul ~lfo when no ~lfo: line exists in the file produces a terminal unresolved-reference error and prevents the graph from swapping in. The fix is to define the bus on its own line above the usage. Bus names always start with ~.

Examples

out: saw 110 >> mul ~lfo with no ~lfo: line — unresolved reference error. Fix: add ~lfo: sin 0.3 >> mul 0.4 >> add 0.5 above.

Assessment

Explain why a reference to ~lfo in a Glicol chain fails when no ~lfo: line exists, and write the two-line snippet that fixes it.