Properly handle `Option<i32>` in `SslRef::set_curves` #863

Job	Run time
Test FIPS integration	2m 58s
Cross build from macOS to Linux (FIPS) (x86_64-unknown-linux-gnu)	5m 49s
clippy	8m 35s
Cross build from macOS to Linux (x86_64-unknown-linux-gnu)	2m 1s
rustfmt	4s
Test features	3m 52s
Test (stable)	2m 20s
Test (arm-android)	2m 19s
Test (arm64-android)	1m 56s
Test (i686-android)	1m 46s
Test (x86_64-android)	2m 4s
Test (aarch64-ios)	2m 10s
Test (aarch64-ios-sim)	2m 8s
Test (x86_64-ios)	2m 24s
Test (i686-linux)	2m 10s
Test (arm-linux)	2m 33s
Test (aarch64-linux)	2m 7s
Test (arm64-macos)	2m 3s
Test (x86_64-macos)	2m 6s
Test (x86_64-mingw)	7m 20s
Test (i686-msvc)	5m 42s
Test (x86_64-msvc)	5m 33s
	1h 10m 0s

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