Don't try to connect to nonexistent controllers (#4939)

Fixes crash on loading presets with controllers.

src/core/ControllerConnection.cpp

@@ -205,7 +205,7 @@ void ControllerConnection::loadSettings( const QDomElement & _this )
 	else
 	{
 		m_controllerId = _this.attribute( "id", "-1" ).toInt();
-		if( m_controllerId < 0 )
+		if( m_controllerId < 0 || m_controllerId >= Engine::getSong()->controllers().size() )
 		{
 			qWarning( "controller index invalid\n" );
 			m_controllerId = -1;