Wrong parameter type in registerFunction

[herki84]

registerFunction in impersonate.js takes an integer as parameter, but document.addEventListener('DOMContentLoaded', registerFunction) supplies an event.
If OCA.Setting is not set at this point, script execution halts due to delay = delay * 2 not working on an object.

Should be an easy fix by including isNaN(delay)

[solracsf]

PRs are welcome 😜