Do not dealloc old value to avoid UB #261

Job	Run time
clippy (ubuntu-latest)	1m 1s
cross (aarch64-unknown-linux-gnu)	1m 27s
clippy (macos-latest)	49s
miri (ubuntu-latest)	4h 38m 11s
cross (aarch64-linux-android)	1m 38s
clippy (windows-latest)	1m 55s
miri (macos-latest)	3h 13m 45s
cross (aarch64-unknown-linux-musl)	1m 38s
rustfmt	18s
cross (i686-linux-android)	1m 52s
sanitizer (ubuntu-latest)	4m 54s
test (ubuntu-latest)	2m 33s
valgrind	4m 45s
cross (x86_64-linux-android)	1m 35s
test (macos-latest)	1m 32s
cross (i686-pc-windows-gnu)	1m 44s
test (windows-latest)	6m 6s
cross (x86_64-pc-windows-gnu)	1m 55s
cross (i686-unknown-linux-gnu)	1m 27s
cross (powerpc64-unknown-linux-gnu)	1m 28s
cross (riscv64gc-unknown-linux-gnu)	1m 25s
cross (wasm32-unknown-unknown)	36s
cross (wasm32-unknown-emscripten)	1m 45s
cargo tarpaulin	7m 5s
	8h 41m 24s

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