Fix ColorTableHarmonizer

[imagejan]

The logic here is inappropriate:

imagej-legacy/src/main/java/net/imagej/legacy/translate/ColorTableHarmonizer.java

Lines 430 to 447 in 5d66b53

	if (luts == null) { // not a CompositeImage
	if (imp.getType() == ImagePlus.COLOR_RGB) {
	for (int i = 0; i < imp.getNChannels() * 3; i++) {
	final ColorTable cTable = ColorTables.getDefaultColorTable(i);
	colorTables.add(cTable);
	}
	}
	else { // not a direct color model image
	final IndexColorModel icm =
	(IndexColorModel) imp.getProcessor().getColorModel();
	ColorTable cTable;
	// if (icm.getPixelSize() == 16) // is 16 bit table
	// cTable = make16BitColorTable(icm);
	// else // 8 bit color table
	cTable = make8BitColorTable(icm);
	colorTables.add(cTable);
	}
	}

because since imagej/ImageJ@6c3e9cd, luts will never be null here.

The logic needs to be adapted to the current behavior of ImagePlus that returns an empty list e.g. for RGB images.