Line 51 of your main.js:
$(
'<div id="titleBar">' +
'<a href="#navPanel" class="toggle"></a>' +
'<span class="title">' + $('#logo').html() + '</span>' +
'</div>'
)
Your titleBar (on small screen) is pulling the html content from your #logo
element. Check to see that there is indeed a #logo
element that exists, or change this call to pull a value form another source.