Checking For An Empty Value

Question

Here's my script:
on run
set AdiumStatus to ""
set AdiumStatusType to ""
tell application "System Events"
count (every process whose name is "Adium")
if result = 1 then
tell application "Adium"
if my status type is available then
set AdiumStatusType to "Available. "
else if my status type is away then
set AdiumStatusType to "Away. "
else if my status type is offline then
set AdiumStatusType to "Offline. "
else if my status type is invisible then
set AdiumStatusType to "Invisible. "
end if
set AdiumStatus to (get my status message)
end tell
end if
end tell
return AdiumStatusType & AdiumStatus
end run
If the user hasn't set a custom message status, the script fails when trying to return "AdiumStatus." How can set the script to where if "my message status" is empty, an empty space is added so it doesn't fail? I tried the following to no avail:
If my status message is not "" then
set AdiumStatus to (get my status message)
end if
But this fails, saying "No result was returned from some part of this expression," and the quotes are highlighted.
Any ideas? And how do I format code I post here, BTW?
Thanks!
Dual 2.0GHz G5   Mac OS X (10.4)  

Answer 1

Nothing at all? Wow, that's pretty impressive. You would appear to be dealing with a broken AppleScript implementation, there; when you request something that doesn't exist, most programs tend to treat that as, you know, an error or something, or at least return the "missing value" value. Returning something that undefines an existing variable isn't reasonable behavior. (Time to file a bug report, methinks.)
One way or another, you're going to have to work around this. Given your result, there, it looks like kel's workaround is the way to go. To put it in the terms of your variables:
tell application "Adium"
set AdiumStatus to my status message
end tell
try
AdiumStatus
on error
set AdiumStatus to missing value
end try
That will give you the status message if it exists, and give you the missing value otherwise. (Which, as I have said, is useful -- when it is time to do something with the result, you can test for it and tell whether the value was set. If you just use an empty string, or some other specific value, then you can't be sure that someone didn't actually set the value to that specific value...) That would look something like this:
if AdiumStatus is missing value then
display dialog "No status message was set."
else
display dialog "The status message was: " & AdiumStatus
end if
The only other workaround which occurs to me would be to rely on the "exists" keyword, as in
if exists my status message then
set AdiumStatus to my status message
else
set AdiumStatus to missing value
end if
but if the application's implementation is already broken enough to return a complete blank without comment, there's no reason to believe it will handle "exists" properly, either.