output/alsa: clear the `period_buffer` in LockCaughtError()

The method Cancel() assumes that the `period_buffer` must be empty when `active==false`, but that is not the case when Play() fails. Of course the assertion in Cancel() is not 100% correct, but I decided to rather fix this in LockCaughtError() because the `period_buffer` should only be accessed from within the RTIO thread, and this is the only code path where `active` can be set to `false` with a non-empty `period_buffer`. Fixes #423

output/alsa: clear the `period_buffer` in LockCaughtError()
3830748d · Max Kellermann · 1a43f514 · 3830748d · 3830748d
Commit 3830748d authored Nov 13, 2018 by Max Kellermann
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NEWS NEWS +2 -0

AlsaOutputPlugin.cxx src/output/plugins/AlsaOutputPlugin.cxx +2 -0

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--- a/NEWS
+++ b/NEWS
 ver 0.21.3 (not yet released)
+* output
+  - alsa: fix crash bug

 ver 0.21.2 (2018/11/12)
 * protocol

--- a/src/output/plugins/AlsaOutputPlugin.cxx
+++ b/src/output/plugins/AlsaOutputPlugin.cxx
@@ -306,6 +306,8 @@ private:
 	}

 	void LockCaughtError() noexcept {
+		period_buffer.Clear();
+
 		const std::lock_guard<Mutex> lock(mutex);
 		error = std::current_exception();
 		active = false;