v3.1.0 getHeaderParams throw split undefined

[lerit]

v 3.0.0: getHeaderParams

name: _.last(_.split(schema.$ref, '/')) || '',

v 3.1.0 getHeaderParams

name: schema.$ref.split('/').pop() || '',

if schema.$ref is undefined,v 3.0.0 still work,but v3.1.0 throw error.
schema get from getParamSchema,when getParamSchema return {},cause this problem