git: remove redundant notes_ref check

[AtariDreams]

Earlier in the init_notes function, notes_ref is guaranteed to be the default ref if it is NULL by then,
making future checks for notes_ref to be redundant, and xstrdup_or_null can just be xstrdup.

[gitgitgadget-git]

There are issues in commit 6f4a6b9:
git: remove redundant notes_ref check
Commit not signed off

[AtariDreams]

/submit

[gitgitgadget-git]

Submitted as pull.1400.git.git.1671399699603.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-git-1400/AtariDreams/xstrdup-v1

To fetch this version to local tag pr-git-1400/AtariDreams/xstrdup-v1:

git fetch --no-tags https://github.com/gitgitgadget/git/ tag pr-git-1400/AtariDreams/xstrdup-v1

[gitgitgadget-git]

This patch series was integrated into seen via 1c46908.

[gitgitgadget-git]

This patch series was integrated into seen via d83ddab.

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This patch series was integrated into seen via 1f4ce63.

[gitgitgadget-git]

This patch series was integrated into seen via 474676c.

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This patch series was integrated into next via 9500384.

[gitgitgadget-git]

This patch series was integrated into seen via 8894347.

[gitgitgadget-git]

This patch series was integrated into seen via 469783e.

[gitgitgadget-git]

This patch series was integrated into seen via 25c60c2.

[gitgitgadget-git]

This patch series was integrated into seen via 1d3f0a9.

[gitgitgadget-git]

This patch series was integrated into seen via f357d46.

[gitgitgadget-git]

This patch series was integrated into master via f357d46.

[gitgitgadget-git]

This patch series was integrated into next via f357d46.

[gitgitgadget-git]

Closed via f357d46.