$installedrank may be undefined when calling metadataupdateflywaytable

[srcshelton]

When placeholder/migration-schema cause a schema-file to be skipped, a message such as:

!> myway::applyschema called myway::metadataupdateflywaytable with mandatory parameter $installedrank undefined - defaulting to '4'

... can be produced - albeit with a sensible value, making this primarily a cosmetic bug... but a bug nonetheless.