Reject len < -1 in ASN1_mbstring_ncopy #269

Job	Run time
zig (ubuntu-24.04-arm, aarch64, Linux)	7m 3s
zig (windows-11-arm, aarch64, Windows)	10m 2s
zig (windows-2022, x86_64, Windows)	12m 19s
zig (ubuntu-latest, x86_64, Linux)	11m 30s
zig (macos-latest, aarch64, Darwin)	9m 3s
	49m 57s

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