Fixed bug where a blank card is displayed

on-tap is attached to both the chip-container and the card.
To know which card gets displayed, the transition function called
by on-tap assigns the selectedAlbum variable the value of the target's
templateInstance.model.item, which is null if the user clicks on any
area which is inside chip-container, but outside a chip. This results
to a blank card being displayed:

![screenshot from 2014-07-16 22 38 47](https://cloud.githubusercontent.com/assets/2637890/3600900/65ce799a-0cfc-11e4-8037-4d1d76654e05.png)

The simplest fix for this is to check if selectedAlbum is null before
setting the page flag to 1.
How about we check for e.target.templateInstance.model.item being undefined and early return here? ie.

```
if (!e.target.templateInstance.model.item) {
  return;
}
```