Bug 63223 Use null to clear message text instead of empty string
I200405200800 StatusLine in jface uses setMessage("") to clear the text while the documentation says you should uset setMessage(null) to clear the text. The code path is slightly different for "" versus null, but using null makes the intent of the caller clearer.
bundles/org.eclipse.jface/src/org/eclipse/jface/action/StatusLine.java
}
    /**
     * Sets an image and error message text to be displayed on the status line.
     * 
     * @param image the image to use, or <code>null</code> for no image
     * @param message the error message, or <code>null</code> for no error message
     */
    public void setErrorMessage(Image image, String message) {
        fErrorText = trim(message);
        fErrorImage = image;
        updateMessageLabel();
    }
    /**
     * Applies the given font to this status line.
     */
    public void setFont(Font font) {
        super.setFont(font);
        Control[] children = getChildren();
        for (int i = 0; i < children.length; i++) {
            children[i].setFont(font);
        }
    }
    /**
     * Sets the message text to be displayed on the status line.
     * The image on the status line is cleared.
     * 
     * @param message the error message, or <code>null</code> for no error message
     */
    public void setMessage(String message) {
        setMessage(null, message);