Don't quit CLI rendering when failed to load sample files

Per #3293 (comment)

Author: PhysSong

src/core/SampleBuffer.cpp

@@ -297,7 +297,6 @@ void SampleBuffer::update( bool _keep_settings )
 		else
 		{
 			fprintf( stderr, "%s\n", message.toUtf8().constData() );
-			exit( EXIT_FAILURE );
 		}
 	}
 }