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.

The simplest fix for this is to check if selectedAlbum is null before
setting the page flag to 1.
Earlier check for null target item

To avoid having nested ifs, the check to see if target item is null
was included in the previous if.
Merge pull request #12 from franzks/master

Fixed bug where a blank card is displayed