Bug 135465 [smoke]An error occurred when new a casading Parameter
Description: An error occurred when new a casading Parameter Step to reproduce: 1.new a sample db data source and data set 2.New a cascading parameter group, named "gp1", 3.select the data set, then create two cascading parameters, one is row["customernumber"], named p1; the other is row["customername"] Actual result; error message occurred repeatly
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
String value = null;
				if ( COLUMN_NAME.equals( property ) )
				{
					if ( element == newParameter )
					{
						value = ""; 
					}
					else
					{
						value = parameter.getName( );
					}
				}
				else if ( COLUMN_VALUE.equals( property ) )
				{
					value = getColumnName( parameter.getValueExpr( ) );
				}
				else if ( COLUMN_DISPLAY_TEXT.equals( property ) )
				{
					value = getColumnName( parameter.getLabelExpr( ) );
				}
				if ( value == null )
				{
					value = ""; 
				}
				return value;
			}
			return ""; 
		}
		public void modify( Object element, String property, Object value )
		{