Bug 145274 __isnull does not work properly when parameters have default value
steps to reproduce: - create a report - add a parameter with default value - preview report in web viewer - modify the url with __null pattern expected behavior: - __null takes effect actual behavior: - it simply didn't
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
String paramValue = configVar.getValue( );
						ScalarParameterHandle parameter = (ScalarParameterHandle) findParameter( paramName );
						
						
						if ( paramValue != null && parameter != null )
						{
							try
							{
								Object paramValueObj = ParameterValidationUtil
										.validate( parameter.getDataType( ),
												parameter.getPattern( ),
												paramValue, ULocale.US );
								paramValue = ParameterValidationUtil
										.getDisplayValue( parameter
												.getDataType( ), parameter
												.getPattern( ), paramValueObj,
												locale );
							}
							catch ( Exception err )
							{
								paramValue = configVar.getValue( );
							}
							this.configMap.put( paramName, paramValue );
						}
					}
				}
				handle.close( );
			}
		}
		catch ( Exception e )