output_thread: check again if output is open on CANCEL

When the player thread unpauses, it sends CANCEL to the output thread,
after having checked that the output is still open.  Problem is when
the output thread closes the device before it can process the CANCEL
command - race condition.  This patch adds another "open" check inside
the output thread.

NEWS

@@ -5,6 +5,7 @@ ver 0.15.5 (2009/??/??)
 * tags:
   - riff, aiff: fixed "limited range" gcc warning
 * decoder_thread: change the fallback decoder name to "mad"
+* output_thread: check again if output is open on CANCEL
 
 
 ver 0.15.4 (2009/10/03)

src/output_thread.c

@@ -257,6 +257,7 @@ static gpointer audio_output_task(gpointer arg)
 
 		case AO_COMMAND_CANCEL:
 			ao->chunk = NULL;
+			if (ao->open)
 				ao_plugin_cancel(ao->plugin, ao->data);
 			ao_command_finished(ao);