add guard clause for alphabet size (#3897) #8415

Job	Run time
.deb packages / ubuntu:24.04	26m 32s
Release linux x86_64 static	5m 29s
.deb packages / ubuntu:22.04	23m 35s
.deb packages / ubuntu:20.04	14m 13s
Windows Build (vcpkg / x86-windows-static)	7m 43s
.deb packages / debian:bullseye	13m 24s
Windows Build (vcpkg / x64-windows-static)	16m 53s
.deb packages / debian:bookworm	13m 27s
Windows Build (vcpkg / x86-windows)	5m 39s
.deb packages / debian:trixie	1m 26s
Windows Build (vcpkg / x64-windows)	8m 5s
.deb packages / debian:sid	12m 41s
	2h 29m 7s

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