Every leo has two copies of every gene, one from mom and one from dad. In this case your leo got a patternless gene from both its parents causing it to show the patternless trait. This trait is recessive to the normal trait (spots), if it had one copy of the normal gene it would express that trait rather than the patternless trait.
The albino gene operates in the same way. Since your gecko is not an albino it got an albino gene from one parent and a gene for normal pigmentation from the other.
Your gecko can only contribute a patternless gene to its offspring. But, since its only het fro albion there is a 50% chance that it will pass on an albino gene and a 50% chance that it will pass on a gene for normal pigmentation.
If you breed him to an albino 50% of the babies will be albino and 50% will be het for albino, but all would be het for patternless.
If you breed him to another patternless het for albino all the babies would be patternless. But, 25% would not have the albino gene at all, 50% would be het for albino, and 25% would be albino patternless.
If you breed him to an albino het for patternless, 25% will be double hets, 25% will be albino het for patternless, 25% will be patternless het for albino and 25% will be patternless albinos.
Hope this helps 
Alice
