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
List columnList = DataUtil.generateComputedColumns( inputElement );
		if ( columnList.size( ) > 0 )
		{
			for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )
			{
				addBinding( (ComputedColumn) iter.next( ) );
			}
		}
		refreshBindingTable( );
	}
	private void refreshBindingTable( )
	{
		bindingTable.refresh( );
		if ( canSelect )
		{
			updateSelection( );
		}
		updateButtons( );
	}
	private void updateButtons( )
	{
		boolean okEnable = false;
		if ( !canSelect || selectedColumnName != null )
		{
			okEnable = true;
		}
		getOkButton( ).setEnabled( okEnable );
		int min = 0;
		int max = bindingTable.getTable( ).getItemCount( ) - 1;
		if ( ( min <= selectIndex ) && ( selectIndex <= max ) )