Bug 299685 Empty iconURI's cause 'MalformedURLException' failures rather than being ignored
One of the issues Lars' found is that if you fill in a field (i.e. iconURI) and subsequently clear it you don't end up in the same model state. Once the value has been set in the editor it will never be 'null' again, clearing the field just sets it to an empty string.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/WBWRenderer.java
return saveableParts;
	}
	private boolean promptForSave(Shell parentShell, MElementContainer<?> window) {
		List<MSaveablePart> saveableParts = collectSaveableParts(window,
				new ArrayList<MSaveablePart>());
		if (!saveableParts.isEmpty()) {
			SaveablePartPromptDialog dialog = new SaveablePartPromptDialog(
					parentShell, saveableParts);
			if (dialog.open() == Window.CANCEL) {
				return false;
			}
			for (Object element : dialog.getCheckedElements()) {
				MSaveablePart part = (MSaveablePart) element;
				Object clientObject = part.getObject();
				try {
					ContextInjectionFactory.invoke(clientObject,
							"doSave", context); 
				} catch (InvocationTargetException e) {
					if (logger != null)
						logger.error(e);
				} catch (CoreException e) {
					if (logger != null)
						logger.error(e);
				}
			}
		}
		return true;
	}
	@Inject
	private IEclipseContext context;