Trying to buy an album without the password should not attempt to authorize the purchase

[Leo Arias]

I'm testing the alecu's branch: https://code.launchpad.net/~alecu/unity-lens-music/musicstore-purchase

When I try to download a song, I'm presented with the Ubuntu One payment confirmation screen. See the attached screenshot.
If I don't enter the password and click the purchase button, the purchase is attempted even when it will fail every time.

So, it would be better if the field was checked before the validation of the password. If the field is empty, show the error immediately.