AUDIO: Add pure virtual MidiDriver::isOpen() method

This in turn enables modifying MidiDriver_MPU401::close() to allow
it to be called on a midi driver that has not yet been opened.

The specific issue that triggered me to make these changes was a
crash-upon-quit in HUGO, caused by it instantiating a midi driver,
then encountering an error (missing hugo.dat) *before* having
opened the new midi driver; the general cleanup code then tries
to close the (not yet opened) midi driver -> kaboom

Also fixed some engines which were leaking MidiDriver instances.

1 files changed, 7 insertions, 1 deletions

diff --git a/engines/made/music.cpp b/engines/made/music.cpp
index 8c9248a262..5ace99788b 100644
--- a/engines/made/music.cpp
+++ b/engines/made/music.cpp
@@ -89,10 +89,16 @@ int MusicPlayer::open() {
 	return 0;
 }
 
+bool MusicPlayer::isOpen() const {
+	return _driver && _driver->isOpen();
+}
+
 void MusicPlayer::close() {
 	stop();
-	if (_driver)
+	if (_driver) {
 		_driver->close();
+		delete _driver;
+	}
 	_driver = 0;
 }