fix: allow templating of null and undefined in a jest each key path template

[Germandrummer92]

Summary

See newly added e2e tests, currently jest crashed with:

 ● allows templating "$array.length"

    Cannot convert undefined or null to object

       7 | });

when adding a nested keypath as a template in a null or undefined object. Instead we just early-exit out of interplation in those cases.

Test plan

• yarn test yarn constraints

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The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: Germandrummer92 / name: Daniel Draper (87febe76ffe9ad85260946f15d9a395e58ae1655, 6ae80f6aa08adad149c8898e63e8cc6c0045922b, 8f6e0a04d3c3d2c2db285c739ef02718604e5825, c67c4bfb81bc8a7eae68c9c07b9e29500a473c73)
• :white_check_mark: login: SimenB / name: Simen Bekkhus (421d9a8fa1d32336364926f4892eec0ad37705fd)

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[Germandrummer92]

hmm, not sure why the tests are now failing 😢

[SimenB]

The one failing test is a known one

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[SimenB]

https://github.com/jestjs/jest/releases/tag/v30.0.0-alpha.4