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/ui/dialogs/ColumnBindingDialog.java
{
	private static final String MSG_ADD = Messages.getString( "ColumnBindingDialog.Text.Add" );
	private static final String MSG_EDIT = Messages.getString( "ColumnBindingDialog.Text.Edit" );
	private static final String MSG_DELETE = Messages.getString( "ColumnBindingDialog.Text.Del" );
	private static final String DEFAULT_COLUMN_NAME = "[result_set_col_name]"; 
	private static final String dummyChoice = "dummy"; 
	public static final String DEFAULT_DLG_TITLE = Messages.getString( "ColumnBindingDialog.DialogTitle" ); 
	private static final String ALL = Messages.getString( "ColumnBindingDialog.All" );
	private static final String NONE_AGGREGATEON = Messages.getString( "ColumnBindingDialog.AGGREGATEON.NONE" );
	private static final String CHOICE_FROM_CONTAINER = Messages.getString( "ColumnBindingDialog.Choice.FromContainer" );
	private static final String CHOICE_NONE = Messages.getString( "ColumnBindingDialog.NONE" );
	private static final String LABEL_COLUMN_BINDINGS = Messages.getString( "ColumnBindingDialog.Label.DataSet" ); 
	private static final String WARN_COLUMN_BINDINGS = Messages.getString( "ColumnBingingDialog.Label.Warn" ); 
	
	
	private static final String COLUMN_NAME = Messages.getString( "ColumnBindingDialog.Column.Name" ); 
	private static final String COLUMN_DATATYPE = Messages.getString( "ColumnBindingDialog.Column.DataType" ); 
	private static final String COLUMN_EXPRESSION = Messages.getString( "ColumnBindingDialog.Column.Expression" ); 
	private static final String COLUMN_AGGREGATEON = Messages.getString( "ColumnBindingDialog.Column.AggregateOn" ); 
	private static final String INPUT_PROPMT = Messages.getString( "ColumnBindingDialog.InputPrompt" ); 
	private static final IChoiceSet DATA_TYPE_CHOICE_SET = DEUtil.getMetaDataDictionary( )
			.getStructure( DataSetParameter.STRUCT_NAME )
			.getMember( DataSetParameter.DATA_TYPE_MEMBER )
			.getAllowedChoices( );
	private static final IChoice[] dataTypes = DATA_TYPE_CHOICE_SET.getChoices( null );