Bug 38729 [Preferences] NPE PreferencePage isValid
getContainer may return null
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferencePage.java
public void createControl(Composite parent) {
		GridData gd;
		Composite content = new Composite(parent, SWT.NULL);
		setControl(content);
		Font font = parent.getFont();
		GridLayout layout = new GridLayout();
		layout.marginWidth = 0;
		layout.marginHeight = 0;
		content.setLayout(layout);
		content.setFont(font);
		
		initializeDialogUnits(content);
		descriptionLabel = createDescriptionLabel(content);
		if (descriptionLabel != null) {
			descriptionLabel.setLayoutData(
				new GridData(GridData.FILL_HORIZONTAL));
		}
		body = createContents(content);
		if (body != null)
			
			body.setLayoutData(new GridData(GridData.FILL_BOTH));
		Composite buttonBar = new Composite(content, SWT.NULL);
		layout = new GridLayout();
		layout.numColumns = 0;
		layout.marginHeight = 0;
		layout.marginWidth = 0;
		buttonBar.setLayout(layout);
		gd = new GridData();
		gd.horizontalAlignment = GridData.END;
		buttonBar.setLayoutData(gd);