Correct a bug that cause a deadlock when deleting BMidi class

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@2009 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/midi/Midi.cpp

@@ -312,10 +312,10 @@ void BMidi::Inflow()
 	{
 		len = read_port(inflowPort, &code, &event, sizeof(event));
 	
-		if (len != sizeof(event)) { continue; }  // ignore errors
-
 		if (code == MSG_CODE_TERMINATE_THREAD) { return; }
 
+		if (len != sizeof(event)) { continue; }  // ignore errors
+
 		switch (event.opcode) 
 		{
 			case BMidiEvent::OP_NONE: