String getInvalidFilenameMessage(String filename) {
		switch (filename) {
			case ".":
			case "..":
				return "Reserved name '" + filename + "'";
			default:
				Matcher m = GhidraFileChooser.INVALID_FILENAME_PATTERN.matcher(filename);
				if (m.find()) {
					return "Invalid characters: " + m.group();
				}
		}
		return null;
	}
SCR 3962 - in this mode we allow the user to press Enter/OK with no text in
the text field, which means to user the current directory as the selected dir
Ghidra/Framework/Docking/src/main/java/docking/widgets/filechooser/GhidraFileChooser.java