ID 460305 - Migration tool: Master Images in the Flix 5 Sequence are blank in Flix 6 due to previous migrations with earlier migration tool versions

Problem summary
During the migration, check that each master is linked to an asset that also contains an artwork media object, in case that master is used in the Panel Browser as well. If it doesn't have one, it should be created

Customer reported version
Flix 6.3.5

Steps to reproduce

1) Migrate from 5 to 6 a Sequence containing Master Images in the Panel Browser itself, using Migration Tool v60 or earlier. The Master Images in the Panel Browser will be blank.

2) Migrate the same Sequence again, in the same Show, using Migration Tool v62. The Master Images in the Panel Browser will still be blank.

Expected behaviour
Version 62 of the Migration Tool comes with support for Master Images in the Sequence itself, so those panels should have artwork.

Actual behaviour
Panels that were Master Images in Flix 5 don't have artwork, because they relink to the initial master imported with the first 5 to 6 migration

Reproduced by support

This bug has been reproduced in:
6.3.5 - Migration Tool v62