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
if (pos == -1) {
				stringToFontData.put(
					key,
					new FontData[] { makeFontData(bundle.getString(key))});
			} else {
				String name = key.substring(0, pos);
				int i = 0;
				try {
					i = Integer.parseInt(key.substring(pos + 1));
				} catch (NumberFormatException e) {
					
					throw new MissingResourceException("Wrong key format ", bundleName, key); 
				}
				FontData[] elements = (FontData[]) stringToFontData.get(name);
				if (elements == null) {
					elements = new FontData[8];
					stringToFontData.put(name, elements);
				}
				if (i > elements.length) {
					FontData[] na = new FontData[i + 8];
					System.arraycopy(elements, 0, na, 0, elements.length);
					elements = na;
					stringToFontData.put(name, elements);
				}
				elements[i] = makeFontData(bundle.getString(key));
			}
		}
	}
}