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 a 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 message, or <code>null</code> for no message
     */
    public void setMessage(Image image, String message) {
        fMessageText = trim(message);
        fMessageImage = image;
        updateMessageLabel();
    }
    /**
     * @see IProgressMonitor#setTaskName(java.lang.String)
     */
    public void setTaskName(String name) {
        fTaskName = name;
    }
    /**
     * Makes the Cancel button visible.
     * @private
     */
    protected void showButton() {
        if (fToolBar != null && !fToolBar.isDisposed()) {
            fToolBar.setVisible(true);
            fToolBar.setEnabled(true);
            fToolBar.setCursor(fStopButtonCursor);
            fCancelButtonIsVisible = true;
        }
    }