If I copy and paste your script in Applescript Editor, I get the message "It's true" or "It's not true". If I paste the same exact script in an Alfred Workflow and run it, I get no message at all.
Here's my workflow with two different actions, "troubleshooting1" and "troubleshooting2": https://dl.dropboxusercontent.com/u/345710/Troubleshooting.alfredworkflow
The "troubleshooting1" action runs your script. Like I mentioned, nothing happens if I run it through Alfred but I get the messages if I run it through Applescript Editor.
The "troubleshooting2" is my script which is supposed to check (for demonstration purposes) whether Safari is active and if it is, it launches TextEdit. If Safari is not active, it is supposed to launch Preview. This is what happens in Applescript Editor. However, both TextEdit and Safari are launched whenever I run the script through Alfred. If I copy and paste the script from Alfred to Applescript Editor, the script again works correctly.
I'm running Alfred 2.0.7 (205) with OSX 10.8.4.