* @return the fallback theme (never <code>null</code>)
*/
protected Theme getFallbackTheme() {
ThemeSource themeSource = RequestContextUtils.getThemeSource(getRequest());
if (themeSource == null) {
themeSource = new ResourceBundleThemeSource();
}
Theme theme = themeSource.getTheme(DEFAULT_THEME_NAME);
if (theme == null) {
throw new IllegalStateException("No theme defined and no fallback theme found");
}