cpal

Fix minor variable mixup #821

Job	Run time
cargo-publish	0s
asmjs-wasm32-test (wasm32-unknown-emscripten)	43s
android-apk-build	1m 46s
android-check	42s
clippy-test	1m 16s
ios-build	4m 40s
linux-check-and-test-armv7	2m 40s
macos-test	1m 32s
rustfmt-check	12s
ubuntu-test	43s
wasm32-wasi-test (wasm32-wasi)	20s
windows-test (x86_64)	2m 3s
wasm32-bindgen-test (wasm32-unknown-unknown)	19s
wasm-beep-build	28s
windows-test (i686)	2m 6s
	19m 30s

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