Fix to UIFocus

@@ -5,11 +5,7 @@ import javax.faces.component.UIComponentBase;
 import javax.faces.component.UIForm;
 import javax.faces.component.UIInput;
 import javax.faces.context.FacesContext;
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Set;
+import java.util.*;
 
 public abstract class UIFocus extends UIComponentBase {
 // ------------------------------ FIELDS ------------------------------
@@ -80,7 +76,10 @@ public abstract class UIFocus extends UIComponentBase {
                 Set<String> allowedClientIds = new HashSet<String>();
                 Iterator<String> clientIdsWithMessages = getFacesContext().getClientIdsWithMessages();
                 while (clientIdsWithMessages.hasNext()) {
-                    allowedClientIds.add(clientIdsWithMessages.next());
+                    final String clientId = clientIdsWithMessages.next();
+                    if (clientId != null) {
+                        allowedClientIds.add(clientId);
+                    }
                 }
                 final List<UIInput> inputs = new ArrayList<UIInput>();
                 getInputs(getParentForm(this), allowedClientIds, inputs);