How do I solve this "Can't continue count" problem in an AppleScript app that deals with parameters?

I'm trying out a simple AppleScript I found online:

on run argv
 set rtn to ((count of argv) as text) & " parameters passed.
The parameters were:
"
 repeat with arg in argv
  set rtn to rtn & "开发者_开发问答      " & (arg as text) & "
"
 end repeat

 return rtn
end run

I saved it as an Application. Everytime I double click it from the Finder, I get the following error popup:

Can't continue count

I can't seem to find any way to solve this.

Running Mac OS X Snow Leopard 10.6.4.

---

When you double-click it you aren't passing any arguments so there's nothing to count... so it errors. You can get around errors with a try block. Try this...

on run argv
    try
        set rtn to ((count of argv) as text) & " parameters passed.
The parameters were:
"
        repeat with arg in argv
            set rtn to rtn & "      " & (arg as text) & "
"
        end repeat
    on error
        set rtn to "There are no arguments to count!"
        display dialog rtn buttons {"OK"} default button 1 with icon note
    end try
    return rtn
end run