title: Mail "Can't continue" for a AppleScript function
body: <p>I'm trying to write an AppleScript for use with Mail (on Snow Leopard) to save image attachments of messages to a folder.  The main part of the AppleScript is:</p>
  
  <pre><code>property ImageExtensionList : {"jpg", "jpeg"}
  property PicturesFolder : path to pictures folder as text
  property SaveFolderName : "Fetched"
  property SaveFolder : PicturesFolder &amp; SaveFolderName
  
  tell application "Mail"
    set theMessages to the selection
    repeat with theMessage in theMessages
      repeat with theAttachment in every mail attachment of theMessage
        set attachmentFileName to theAttachment's name
        if isImageFileName(attachmentFileName) then
          set attachmentPathName to SaveFolder &amp; attachmentFileName
          save theAttachment in getNonexistantFile(attachmentPathName)
        end if        
      end repeat
    end repeat
  end tell
  
  on isImageFileName(theFileName)
    set dot to offset of "." in theFileName
    if dot &gt; 0 then
      set theExtension to text (dot + 1) thru -1 of theFileName
      return theExtension is in ImageExtensionList
    end if
    return false
  end isImageFileName
  </code></pre>
  
  <p>When run, I get the error:</p>
  
  <blockquote>
    <p>error "Mail got an error: Can’t continue isImageFileName." number -1708</p>
  </blockquote>
  
  <p>where error -1708 is:</p>
  
  <blockquote>
    <p>Event wasnt handled by an Apple event handler.</p>
  </blockquote>
  
  <p>However, if I copy/paste the <code>isImageFileName()</code> into another script like:</p>
  
  <pre><code>property ImageExtensionList : {"jpg", "jpeg"}
  
  on isImageFileName(theFileName)
    set dot to offset of "." in theFileName
    if dot &gt; 0 then
      set theExtension to text (dot + 1) thru -1 of theFileName
      return theExtension is in ImageExtensionList
    end if
    return false
  end isImageFileName
  
  if isImageFileName("foo.jpg") then
    return true
  else
    return false
  end if
  </code></pre>
  
  <p>it works fine.  Why does Mail complain about this?</p>