Call setViewer() for all ConverterSetups when opening a BDV.

This was an oversight from when the RealARGBColorConverterSetup
setViewer() method was moved to the ConverterSetup interface.

src/main/java/bdv/BigDataViewer.java

@@ -342,8 +342,7 @@ public class BigDataViewer
 		viewer = viewerFrame.getViewerPanel();
 
 		for ( final ConverterSetup cs : converterSetups )
-			if ( RealARGBColorConverterSetup.class.isInstance( cs ) )
-				( ( RealARGBColorConverterSetup ) cs ).setViewer( viewer );
+			cs.setViewer( viewer );
 
 		manualTransformation = new ManualTransformation( viewer );
 		manualTransformationEditor = new ManualTransformationEditor( viewer, viewerFrame.getKeybindings() );