Bug 131771 Match animated message behaviour in Preferences
An enhancement should be made to Preferences so that warnings and errors show up in a sliding message area like it they do in TitleAreaDialog.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/TitleAreaDialog.java
* and will be redisplayed when the error message is set to
     * <code>null</code>.
     * 
     * @param newErrorMessage
     *            the newErrorMessage to display or <code>null</code>
     */
    public void setErrorMessage(String newErrorMessage) {
        
        if (errorMessage == null ? newErrorMessage == null : errorMessage
                .equals(newErrorMessage)) {
			return;
		}
        errorMessage = newErrorMessage;
         
        
        if (errorMessage == null) {
        	if(messageArea != null && !showingWarning){
           		setMessageAreaVisible(false);
         	}
            if (showingError) {
                
                showingError = false;
            }
            
            
            
            
            if (message == null) {
                
                message = "";