Bug 20474 [Dialogs] SelectionDialog should not return an initial selection of null
F3 The JavaDoc for SelectionDialog.getInitialSelection does not state that null is a valid return value. If we think that clients are acutally using the null case to avoid performing some real work then we should fix the javadoc. Otherwise we should an empty list.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/dialogs/MultiElementListSelectionDialog.java
* @see Dialog#createDialogArea(Composite)
	 */	
	protected Control createDialogArea(Composite parent) {
		Composite contents= (Composite) super.createDialogArea(parent);
		createMessageArea(contents);
		createFilterText(contents);
		createFilteredList(contents);
		fCurrentPage= 0;
		setPageData();
		
		return contents;
	}
	/**
	 * @see Dialog#createButtonsForButtonBar(Composite)
	 */
	protected void createButtonsForButtonBar(Composite parent) {
		fBackButton= createButton(parent, IDialogConstants.BACK_ID, IDialogConstants.BACK_LABEL, false);
		fNextButton= createButton(parent, IDialogConstants.NEXT_ID, IDialogConstants.NEXT_LABEL, true);
		fFinishButton= createButton(parent, IDialogConstants.OK_ID, IDialogConstants.FINISH_LABEL, false);
		createButton(parent, IDialogConstants.CANCEL_ID, IDialogConstants.CANCEL_LABEL, false);
	}
	
	/**
	 * @see SelectionDialog#createMessageArea(Composite)
	 */
	protected Label createMessageArea(Composite parent) {
		Composite composite= new Composite(parent, SWT.NONE);
		GridLayout layout= new GridLayout();
		layout.marginHeight= 0;
		layout.marginWidth= 0;