fix(Conflict detection): account for pre-existing auto-save items

Feliksas Mazeikisrequested to merge
issue/canvas-3589076:3589076-issue-branch into 1.x

Prevents conflict detection on pre-existing auto-save items with no original_hash property.

Testing instructions

  • First step for someone to test the changes in this MR

Closes #3589076

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