Spell Book Multicast

[Kam]

When I have multiple units with the same spell-book selected and one of them does not have enough mana to cast a spell within the book none of them will cast.

http://www.hiveworkshop.com/forums/pastebin_data/y801wp/SBNoCast.jpg

How do I resolve this?

 

[rulerofiron99]

Make a dummy spell that costs 0 mana and does nothing.

 

[Kam]

How would that solve the issue?

Would it not simply cast the do nothing spell? I need to cast spells just as you would normally with a group of same-unit units.