Fix slicing struct init array field with ArrayLiteralExpression.basis set

[ntrel]

Fixes #22699.

Thanks to @oCHIKIo for finding the fix.

[dlang-bot]

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Testing this PR locally

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dub run digger -- build "master + dmd#22807"

[ibuclaw]

OK for targeting stable.

[oCHIKIo]

Thanks for putting the PR together @ntrel, glad I could help track down the fix! And thanks @ibuclaw for the review.