Unwanted popup from applet

set pathToFileWork to "HD:Users:USER:Desktop:File.rtf"
set pathToFolderBackups to "HD:Users:USER:Desktop:Folder:"

try -- trap Finder duplicate error
	tell application id "MACS" to set Dup to duplicate alias pathToFileWork to folder pathToFolderBackups
end try

When run from the Editor all is well: after the 1st run the error is suppressed.
However, when run as an applet an alert pops up after the 1st run, asking if I want to overwrite | stop | keep both.
This is what an application should do, but it seems it happens outside AppleScript, as the try block is ignored.
I’m thinking I should test for the presence of a duplicate, instead of using a try block.
Is there another solution?

(The actual script with this code keeps running after I dismiss the alert, but I just don’t want to see it.)

I find the applet suppresses the error if it explicitly specifies duplicating without replacing (which I presume is the intention):

local pathToFileWork, pathToFolderBackups, Dup

set pathToFileWork to "HD:Users:USER:Desktop:File.rtf"
set pathToFolderBackups to "HD:Users:USER:Desktop:Folder:"

try -- trap Finder duplicate error
	tell application id "MACS" to set Dup to duplicate alias pathToFileWork to folder pathToFolderBackups without replacing
end try

It is, yes.
Thanks for the heads up re dictionaries.