updating values leads to nullpointer error message when having a typo

[marekzan]

While using the following option

updateValues : [[fieldPath: "image.name", newValue: imageName]]

The Jenkins logs yield a generic nullpointer error: "cannot set value of null object"

It would be more clear, if the error message would be something like "the field 'image.name' was not found and could therefore not be set with the new value.