FieldGroup.commit throws NPE if not bound to an item (#14732).

Added null check and corresponding test.

Change-Id: I197dad14d6b5f7bf9bedcdf083d4b1f0f20efdcd

server/src/com/vaadin/data/fieldgroup/FieldGroup.java

@@ -436,8 +436,14 @@ public class FieldGroup implements Serializable {
             return;
         }
         for (Field<?> f : fieldToPropertyId.keySet()) {
-            ((Property.Transactional<?>) f.getPropertyDataSource())
-                    .startTransaction();
+            Property.Transactional<?> property = (Property.Transactional<?>) f
+                    .getPropertyDataSource();
+            if (property == null) {
+                throw new CommitException("Property \""
+                        + fieldToPropertyId.get(f)
+                        + "\" not bound to datasource.");
+            }
+            property.startTransaction();
         }
         try {
             firePreCommitEvent();

server/tests/src/com/vaadin/data/fieldgroup/FieldGroupExceptionTest.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.data.fieldgroup;
+
+import org.junit.Test;
+
+import com.vaadin.data.fieldgroup.FieldGroup.CommitException;
+import com.vaadin.ui.PopupDateField;
+
+public class FieldGroupExceptionTest {
+
+    @Test(expected = CommitException.class)
+    public void testUnboundCommitException() throws CommitException {
+        FieldGroup fieldGroup = new FieldGroup();
+        PopupDateField dateField = new PopupDateField();
+        fieldGroup.bind(dateField, "date");
+        fieldGroup.commit();
+    }
+
+}