PKG can't silent install on Mac Os 10.5

I have made an Installer by PackageMaler3.0.6 on Mac OS 10.8. Also I have add a JavaScript function in Distribution,This function use for detect the certain App is running or not. Some code like this:

var allProcess = new Array();

allProcess = system.applications.all();

var allProcessCount = allProcess.length;

...

If I normally install (With Installer UI) this pkg on 10.8,10.7,10.5, it's Ok, all function works fine. If i use command line to silent install On 10.8,10.7 it's OK, no error. But if i silent install on 10.5.8, there will be an error in terminal(JavaScript error), can't install. If i remove the code of "var allProcessCount = allProcess.length;" It can silent install on 10.5.8, once if added the code like "allProcess.length" ,there will be an error,it seemed can't use the array property in silent install on 10.5, but 10.7,10.8 it's OK and install with UI it's also Ok on 10.5. Did anyone knows how can i slove this issue? Thanks!!!