Q: What are these "(null)" listings in my iCall contacts?
A: iCall contact listings that display as "(null)" are contact entries that have been automatically imported from your iPhone contacts that do not currently have a first and/or last name included in the entry. This most often happens when email addresses are automatically added to your iPhone's contacts via Gmail or iPhone's mail program. In both instances the email address will be added to your contacts automatically, but without a first or last name entry.
Resolution: either delete the contact in question from you iPhone contacts, OR find the contact(s) in question and add a first and/or last name.