Photoshop, copy layer from one open document

So I am trying to copy one layer to another with applescript but I can't select the document I want to copy it to.

tell application id "com.adobe.photoshop"
  activate
  set starter_image to name of current document
  log starter_image
  set AppleScript's text item delimiters to {".jpg"}
  set Destination_Image to (first text item of starter_image) & "_2.jpg"
  log Destination_Image
  tell current document
  set Main_Image to layer "Main Image"
  select all
  copy selection
  end tell
  set current document to Destination_Image
end tell

The result is this

tell application "Adobe Photoshop CC 2018"
  activate
  get name of current document
  --> "MM--MKY000050WH.JPG"
  (*MM--MKY000050WH.JPG*)
  (*MM--MKY000050WH_2.jpg*)
  get layer "Main Image" of current document
  --> art layer 1 of document "MM--MKY000050WH.JPG"
  select all current document
  --> current application
  copy selection of current document
  --> current application
  set current document to "MM--MKY000050WH_2.jpg"
  --> error "Object expected" number 1333
Result:
error "Adobe Photoshop CC 2018 got an error: Object expected" number 1333

How can I switch to the other document please?