Update check to see if dataTarget is undefined
Update check to see if dataTarget is undefined

- Improve readability, as typeof undefined will always result in the
string 'undefined'

joelanman/govuk_elements,alphagov/govuk_elements,gavboulton/govuk_elements,joelanman/govuk_elements,TFOH/govuk_elements,gavboulton/govuk_elements,alphagov/govuk_elements,gavboulton/govuk_elements,alphagov/govuk_elements,gavboulton/govuk_elements,TFOH/govuk_elements,alphagov/govuk_elements