Bug 53881 [Colors] Color/Gradient registry should return default values.
There should be default values for when a user does .get() on a bad key.
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/FontRegistry.java
*  Font font = registry.get("textfont");
	 *  control.setFont(font);
	 *  ...
	 * </pre>
	 *
	 * @param location the name of the resource bundle
	 * @param the ClassLoader to use to find the resource bundle
	 * @exception MissingResourceException if the resource bundle cannot be found
	 * @since 2.1
	 */
	public FontRegistry(String location, ClassLoader loader)
		throws MissingResourceException {
		Display display = Display.getCurrent();
		Assert.isNotNull(display);
		
		
		readResourceBundle(location);
		hookDisplayDispose(display);
	}
	/**
	 * Load the FontRegistry using the ClassLoader from the PlatformUI
	 * plug-in
	 */
	public FontRegistry(String location) throws MissingResourceException {
		
		
		this(location, null);
	}
	/**
	 * Read the resource bundle at location. Look for a file with the