Bug 155365 Can not set data type to "date time" when editing "Data Item"
Description: Can not set data type to "date time" when editing "Data Item" Steps to reproduce: 1. Insert a data item to the layout 2. Name it and set the expression to "a = new Date()" 3. Select the data type to date time 4. Press ok Actual result: An Birt Exception is thrown out. Expected result: No NPE thrown out
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dialogs/DataItemBindingDialog.java
WidgetUtil.createGridPlaceholder( composite, 1, false );
		new Label( composite, SWT.NONE ).setText( EXPRESSION );
		itemExpression = new Text( composite, SWT.BORDER );
		itemExpression.setLayoutData( new GridData( GridData.FILL_HORIZONTAL
				| GridData.GRAB_HORIZONTAL ) );
		Button expressionButton = new Button( composite, SWT.PUSH );
		expressionButton.setText( "..." );
		expressionButton.setLayoutData( new GridData( ) );
		expressionButton.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )
			{
				handleExpressionButtonSelectEvent( );
			}
		} );
		itemExpression.addModifyListener( new ModifyListener( ) {
			public void modifyText( ModifyEvent e )
			{
				if ( ExpressionUtil.hasAggregation( itemExpression.getText( ) ) )
				{
					String groupType = DEUtil.getGroupControlType( input );
					if ( !( bindingColumn != null
							&& bindingColumn.getExpression( ) != null && bindingColumn.getExpression( )
							.equals( itemExpression.getText( ) ) ) )
					{
						if ( groupType.equals( DEUtil.TYPE_GROUP_GROUP ) )
						{
							setAggregateOnSelect( ( (GroupHandle) DEUtil.getGroups( input )
									.get( 0 ) ).getName( ) );
						}
						else if ( groupType.equals( DEUtil.TYPE_GROUP_LISTING ) )