setting 'icon' to an existing iconfile results in 'TypeError'

[gretel]

on node v10.17.0:

TypeError: Cannot read property 'call' of undefined
    at CpFileError.get (/somepath/node_modules/nested-error-stacks/index.js:22:52)
    at /somepath/node_modules/gulp-util/lib/PluginError.js:45:35
    at Array.forEach (<anonymous>)
    at new PluginError (/somepath/node_modules/gulp-util/lib/PluginError.js:44:8)
    at EventEmitter.<anonymous> (/somepath/node_modules/gulp-appdmg/index.js:20:26)
    at EventEmitter.emit (events.js:198:13)
    at EventEmitter.emit (domain.js:448:20)
    at /somepath/node_modules/appdmg/lib/pipeline.js:102:10
    at /somepath/node_modules/appdmg/lib/pipeline.js:29:9
    at Pipeline.runRemainingCleanups (/somepath/node_modules/appdmg/lib/pipeline.js:74:45)

does not matter wether the file exists or not - only removing the property helps.

thanks for checking