Can't get this droplet to save a JPEG...

Question

I'm getting an error that it can't find the document after it's opened. The actions seem to run just fine, but it stops short of actually saving the file into the newly created folder. It also doesn't close the last document.
Can anyone find a problem with my script? I seem to have hit a brick wall here.
(I'm running Photoshop CS6.)
on open mgItems
     set myDate to (get current date)
     set y to year of myDate as text
     set m to month of myDate as integer
     set d to day of myDate as integer
     if d < 10 then
          set d to "0" & d as text
     else
          set d to d as text
     end if
     if m < 10 then
          set m to "0" & m as text
     else
          set m to m as text
     end if
set y to text -2 thru -1 of y
set myReleaseDate to y & m & d & "_iPadResized"
repeat with mgThisItem in mgItems
     tell application "System Events"
          set targetFolderPath to path of container of disk item (mgThisItem as text)
     end tell
     tell application "Adobe Photoshop CS6"
          activate
          try
               open mgThisItem
          set mgDocName to name of current document
          set text item delimiters of AppleScript to ".tif"
          set mgShortName to text item 1 of mgDocName
          set mgPackageFilePath to targetFolderPath & myReleaseDate
          my createFolders(POSIX path of file (mgPackageFilePath))
          set display dialogs to never
          set thisdoc to current document
          set docHeight to height of thisdoc
          set docWidth to width of thisdoc
          tell thisdoc
               flatten document
               if docHeight / docWidth > 0.75 then
                    do action "iPad_tall" from "iPad Resize"
               else
                    do action "iPad_wide" from "iPad Resize"
               end if
               save in file mgPackageFilePath as JPEG with options {quality:12}
          end tell
          close the current document saving no
       on error e
            display dialog e
       end try
  end tell
end repeat
display dialog "Files resized for iPad"
end open
on createFolders(pathString)
     do shell script "mkdir -p " & quoted form of pathString
end createFolders

Answer 1

You can save applescript files as a droplet that acts as a standalone application. This means that I select a list of files and drag them onto the droplet, activating the script.
So yes, it's a droplet, and it's also Applescript.
The code is fairly straightforward, which is why I'm confused!