spire controller superfluous projectile issue

[smoth]

[f=0016027] Error: LuaRules::RunCallIn: error = 2, RecvLuaMsg, [Internal Lua error: Call failure] [string "LuaRules/Gadgets/unit_spire_controller.lua"]:203: bad argument #4 to 'SetProjectileTarget' (number expected, got nil)