When making macros like that you need some syntax to make it know if the target exists or not (exists, harm, help, etc.)
Ex:
Code:
#showtooltip
/cast [target=mouseover, harm] Living Bomb; Living Bomb
Same with other "target"-commands such as "focus" or "targettarget". With all of theese you need a line to verify the existance of that target (in the example it's 'harm').
I use this on mainly all my spells as an elem shaman.
Code:
#showtooltip
/cast [harm] Lightning Bolt; Healing Wave
Or as resto shaman
Code:
#showtooltip
/cast [target=focus, help] Earth Shield;