[MTG] Use MagicCardInfo card number as fallback when a card doesn't have a number listed
[MTG] Use MagicCardInfo card number as fallback when a card doesn't have a number listed

This is needed because 'mtglink' uses the card number to construct the MagicCardInfo link
They already use the same cardnumber as Wizards when the 'number' field does exist, so it should be accurate enough for a fallback value

Didero/DideRobot