Resample SampleBuffer only once when loading from SampleClip (#6594)

The SampleBuffer's sample rate in SampleClip was altered twice during
SampleClip::loadSettings: first when setSampleFile was called,
which set the sample rate of the SampleBuffer to the AudioEngine's
sample rate (good), and a second time when calling setSampleRate,
which set it to the sample rate specified within the project file (bad).
This led to the sample rate of the buffer being different than that of
the project, resulting in it being pitched incorrectly on playback.

src/core/SampleClip.cpp

@@ -292,15 +292,15 @@ void SampleClip::loadSettings( const QDomElement & _this )
 	if( sampleFile().isEmpty() && _this.hasAttribute( "data" ) )
 	{
 		m_sampleBuffer->loadFromBase64( _this.attribute( "data" ) );
+		if (_this.hasAttribute("sample_rate"))
+		{
+			m_sampleBuffer->setSampleRate(_this.attribute("sample_rate").toInt());
+		}
 	}
 	changeLength( _this.attribute( "len" ).toInt() );
 	setMuted( _this.attribute( "muted" ).toInt() );
 	setStartTimeOffset( _this.attribute( "off" ).toInt() );
 
-	if ( _this.hasAttribute( "sample_rate" ) ) {
-		m_sampleBuffer->setSampleRate( _this.attribute( "sample_rate" ).toInt() );
-	}
-
 	if( _this.hasAttribute( "color" ) )
 	{
 		useCustomClipColor( true );