upgrade TODC Bootstrap to bootstrap 3.2.0 (google theme)

bootstrap-core/src/main/java/de/agilecoders/wicket/core/settings/DefaultThemeProvider.java

@@ -6,13 +6,22 @@
 import org.apache.wicket.util.string.Strings;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
+ * # Description
+ *
  * A default {@link ThemeProvider} implementation that only contains
  * the {@link de.agilecoders.wicket.core.markup.html.themes.bootstrap.BootstrapTheme}.
  *
- * @author miha
+ * # Usage
+ *
+ * ```java
+ * settings.setThemeProvider(new DefaultThemeProvider(settings));
+ * ```
+ *
+ * @author Michael Haitz <[email protected]>
  */
 public class DefaultThemeProvider implements ThemeProvider {
 
@@ -106,7 +115,7 @@ public DefaultThemeProvider defaultTheme(final ITheme theme) {
     public DefaultThemeProvider defaultTheme(final String themeName) {
         ITheme newDefaultTheme = byName(themeName);
 
-        if (defaultTheme != newDefaultTheme) {
+        if (newDefaultTheme != null && !newDefaultTheme.equals(defaultTheme)) {
             defaultTheme = newDefaultTheme;
         }
 
@@ -128,7 +137,7 @@ public ITheme byName(String name) {
 
     @Override
     public List<ITheme> available() {
-        return new ArrayList<ITheme>(themes);
+        return Collections.unmodifiableList(themes);
     }
 
     @Override