Bug 35192 Dialog.applyDialogFont should protect itself against null arguments
RC2 Now that many plugins use this method to apply the dialog font to widgets the method should protect itself against null arguments. Normally clients create their widget tree in a method createControl and there are changes that the returned control might be null. Adding a statement Dialog.applyDialogFont (result) with result == null will result in new NPEs.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
* The <code>Dialog</code> implementation of this framework method
	 * lays out a button bar and calls the <code>createButtonsForButtonBar</code>
	 * framework method to populate it. Subclasses may override.
	 * </p>
	 * <p>
	 * The returned control's layout data must be an instance of 
	 * <code>GridData</code>.
	 * </p>
	 * 
	 * @param parent the parent composite to contain the button bar
	 * @return the button bar control
	 */
	protected Control createButtonBar(Composite parent) {
		Composite composite = new Composite(parent, SWT.NONE);
		
		GridLayout layout = new GridLayout();
		layout.numColumns = 0; 
		layout.makeColumnsEqualWidth = true;
		layout.marginWidth =
			convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
		layout.marginHeight =
			convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
		layout.horizontalSpacing =
			convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
		layout.verticalSpacing =
			convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);
		composite.setLayout(layout);
		GridData data =
			new GridData(
				GridData.HORIZONTAL_ALIGN_END | GridData.VERTICAL_ALIGN_CENTER);