fix fuzzed issue in gix-config #3850

Job	Run time
lint	3m 36s
cargo-deny (advisories)	32s
installation (win-msvc)	6m 43s
cargo-deny (bans licenses sources)	32s
pure-rust-build	1m 59s
installation (win-gnu)	6m 22s
test-32bit (armv7-linux-androideabi)	1m 8s
test	20m 22s
installation (win32-msvc)	5m 50s
installation (win32-gnu)	7m 12s
test-fast (windows-latest)	12m 46s
test-fast (macos-latest)	7m 31s
WebAssembly (wasm32-unknown-unknown)	55s
test-fast (ubuntu-latest)	3m 14s
WebAssembly (wasm32-wasi)	35s
	1h 19m 17s

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