thread/Thread: throw std::system_error on error

src/player/Thread.cxx

@@ -26,7 +26,6 @@
 #include "MusicBuffer.hxx"
 #include "MusicChunk.hxx"
 #include "DetachedSong.hxx"
-#include "system/FatalError.hxx"
 #include "CrossFade.hxx"
 #include "Control.hxx"
 #include "output/MultipleOutputs.hxx"
@@ -1235,7 +1234,5 @@ StartPlayerThread(PlayerControl &pc)
 {
 	assert(!pc.thread.IsDefined());
 
-	Error error;
-	if (!pc.thread.Start(player_task, &pc, error))
-		FatalError(error);
+	pc.thread.Start(player_task, &pc);
 }