title: Using popPage() causes NavigatorView's page stack is empty error
body: <p>I'm very new to OnsenUI and am using v1.1.4 along with PhoneGap/Cordova. I have a lot of <code>ons-page</code> files in my project and I use <code>pushPage</code> a lot. However, I am unable to <code>popPage()</code>. I've tried to debug this on my own and I see that the pages are properly pushed onto the stack (goes from page length of 1 to 2 each time a page is pushed). However, the error message <code>NavigatorView's page stack is empty</code> always shows up whenever I try to pop a page. What could be going wrong?</p>
  
  <p>Side question: Does the page length never exceed 2? </p>