I was trying to run the demo project that has the emailSkypePhoneSMS (see attached) - it was giving me this error and displayed a blank page:
So I added this to the project property Xpert > HTML:
phone.style.display = "none"
Now it displays the form and when I enter my phone (no dashes) into the phone textbox and click Phone button, it brings up my phone, has a button that says “Call undefined”. I click that and it dials 863-334-633 and says your call cannot be completed as dialed.