Reduce uses of uninitialized arrays #4645

Job	Run time
build-windows (cargo-build, x86_64-pc-windows-msvc)	12m 32s
build-macos (Cargo build (x64), cargo-build, x86_64-apple-darwin)	5m 27s
rustfmt-clippy	2m 30s
build-windows (cargo-test, x86_64-pc-windows-msvc)	12m 33s
build-unix (beta-build)	3m 31s
build-macos (Cargo test (x64), cargo-test, x86_64-apple-darwin)	6m 24s
build-windows (cargo-c, x86_64-pc-windows-gnu)	13m 29s
build-macos (Cargo C-build (x64), cargo-c, x86_64-apple-darwin)	7m 11s
build-unix (1.70.0-tests)	3m 31s
build-macos (Cargo build (Arm64), cargo-build, aarch64-apple-darwin)	5m 25s
build-unix (aom-tests)	3m 31s
build-macos (Cargo C-build (Arm64), cargo-c, aarch64-apple-darwin)	7m 20s
build-unix (dav1d-tests)	3m 31s
build-unix (no-asm-tests)	3m 31s
build-unix (grcov-codecov)	3m 12s
build-unix (bench)	3m 31s
build-unix (doc)	2m 47s
build-unix (cargo-c)	3m 29s
build-unix (check-no-default)	2m 0s
build-unix (check-extra-feats)	3m 32s
build-unix (check-unstable-feats)	3m 14s
build-unix (fuzz)	3m 35s
build-unix (dav1d-tests-arm64, stable)	3m 34s
	1h 59m 20s

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