Non-ASCII background names pass through the Quattro upgrade
A change merged into quattro reads background paths without quoting, so a non-ASCII name such as café.jpg does not stop the Quattro upgrade.
git ls-files quotes paths with non-ASCII bytes by default, so a user background such as café.jpg comes out quoted and escaped. The move then fails, and the upgrade stops partway through the user-config step.
Reading the list with a NUL delimiter gives the raw path. The same file then moves, and the upgrade continues.