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
layout.horizontalSpacing = 0;
        layout.verticalSpacing = 0;
        layout.marginHeight = 0;
        layout.marginWidth = 0;
        fProgressBarComposite.setLayout(layout);
        fProgressBar = new ProgressIndicator(fProgressBarComposite);
        fProgressBar.setLayoutData(new GridData(GridData.GRAB_HORIZONTAL
                | GridData.GRAB_VERTICAL));
        fStopButtonCursor = new Cursor(getDisplay(), SWT.CURSOR_ARROW);
    }
    /**
     * Notifies that the main task is beginning.
     * 
     * @param name the name (or description) of the main task
     * @param totalWork the total number of work units into which
     * the main task is been subdivided. If the value is 0 or UNKNOWN the 
     * implemenation is free to indicate progress in a way which doesn't 
     * require the total number of work units in advance. In general users 
     * should use the UNKNOWN value if they don't know the total amount of
     * work units. 
     */
    public void beginTask(String name, int totalWork) {
        final long timestamp = System.currentTimeMillis();
        fStartTime = timestamp;
        final boolean animated = (totalWork == UNKNOWN || totalWork == 0);
        
        
        Runnable timer = new Runnable() {
            public void run() {
                StatusLine.this.startTask(timestamp, animated);