Fix Grid trying to sort Container that is not Sortable (#16311)

Change-Id: I0159a068549d563f8d1b8378730a383f14700353

server/src/com/vaadin/ui/Grid.java

@@ -2858,10 +2858,8 @@ public class Grid extends AbstractComponent implements SelectionNotifier,
 
             sort(false);
         } else {
-
-            // If the new container is not sortable, we'll just re-set the sort
-            // order altogether.
-            clearSortOrder();
+            // Clear sorting order. Don't sort.
+            sortOrder.clear();
         }
 
         datasourceExtension = new RpcDataProviderExtension(container);

server/tests/src/com/vaadin/tests/server/component/grid/GridContainerNotSortableTest.java

@@ -0,0 +1,56 @@
+/*
+ * 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.tests.server.component.grid;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import org.junit.Test;
+
+import com.vaadin.data.Item;
+import com.vaadin.data.Property;
+import com.vaadin.data.util.AbstractInMemoryContainer;
+import com.vaadin.ui.Grid;
+
+public class GridContainerNotSortableTest {
+
+    @Test
+    public void testGridWithNotSortableContainer() {
+        new Grid(new AbstractInMemoryContainer<Object, Object, Item>() {
+
+            @Override
+            public Collection<?> getContainerPropertyIds() {
+                return Collections.EMPTY_LIST;
+            }
+
+            @Override
+            public Property getContainerProperty(Object itemId,
+                    Object propertyId) {
+                return null;
+            }
+
+            @Override
+            public Class<?> getType(Object propertyId) {
+                return null;
+            }
+
+            @Override
+            protected Item getUnfilteredItem(Object itemId) {
+                return null;
+            }
+        });
+    }
+}