fix range error with -mscrtlib=

[rainers]

The range error doesn't trigger in released versions because they are built without boundschecks.

[dlang-bot]

Thanks for your pull request, @rainers!

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Testing this PR locally

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dub fetch digger
dub run digger -- build "master + dmd#10408"

[Geod24]

Another hint that an array in a boolean context should check length and not .ptr.
Looks like this fails tho.

[rainers]

Another hint that an array in a boolean context should check length and not .ptr.

Both are tested and have to be 0/null for the boolean to be false.

Looks like this fails tho.

Looks unrelated, This build has the same problem: https://dev.azure.com/dlanguage/dmd/_build/results?buildId=4590