ByteField getField(BigInteger index, int fieldNum) {
		if (indexMap != null) {
			if (fieldNum < fieldFactories.length) {
				return (ByteField) fieldFactories[fieldNum].getField(index);
			}
		}
		return null;
	}
Translates a screen/view selection into a byte block model selection
@param fieldSelection a {@link FieldPanel} selection
@return a {@link ByteBlockSelection}
Ghidra/Features/ByteViewer/src/main/java/ghidra/app/plugin/core/byteviewer/ByteViewerComponent.java