Adjust "Diffable" to exclude missing target objects #100

Job	Run time
Check	3m 52s
Deny (advisories)	45s
Build (ubuntu-latest, x86_64-unknown-linux-gnu, linux-x86_64, libgtk-3-dev)	8m 18s
Deny (bans licenses sources)	37s
Test (ubuntu-latest)	6m 33s
Build (windows-latest, x86_64-pc-windows-msvc, windows-x86_64)	10m 41s
Test (windows-latest)	7m 11s
Build (macos-latest, x86_64-apple-darwin, macos-x86_64)	7m 27s
Test (macos-latest)	5m 55s
Build (macos-latest, aarch64-apple-darwin, macos-arm64)	7m 30s
Release	0s
	58m 49s

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