[skip changelog] Fix lib install crash on nightlies

[silvanocerza]

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• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)

• What kind of change does this PR introduce?

Fixes a crash happening only on nightly releases.

• What is the current behavior?

Calling lib install with --zip-path or --git-url flag and config library.enable_unsafe_install set to false on a nightly build makes the CLI crash.

• What is the new behavior?

Calling lib install with --zip-path or --git-url flag and config library.enable_unsafe_install set to false on a nightly build doesn't crash the CLI anymore.

• Does this PR introduce a breaking change, and is
  titled accordingly?

Nope.

• Other information:

Fixes #1196.

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