fix

git-svn-id: http://svn.net-core.org/repos/t-engine4@6092 51575b47-30f0-44d4-a5cc-537603b46e54

game/engines/default/engine/Target.lua

@@ -419,6 +419,8 @@ end
 function _M:scan(dir, radius, sx, sy, filter)
 	sx = sx or self.target.x
 	sy = sy or self.target.y
+	if not sx or not sy then return end
+	
 	radius = radius or 20
 	local actors = {}
 	local checker = function(_, x, y)