Fix lock_on_merge migration

What does this MR do and why?

For GDK versions who updated in the last few hours since !128667 (merged) merged, it results in an error since the previous migration !127683 (merged) was no-op in !128570 (merged) rather than destroyed.

This also fixes a potential issue when the previous MR !128667 (merged) hits staging .

Changelog: fixed

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