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
{
					
					if ( ParameterAccessor.SERVLET_PATH_RUN
							.equalsIgnoreCase( request.getServletPath( ) ) )
					{
						this.exception = e;
						break;
					}
				}
			}
			else
			{
				params.put( paramName, null );
			}
		}
		return params;
	}
	/**
	 * get parameter object.
	 * 
	 * @param request
	 *            HttpServletRequest
	 * @param parameter
	 *            ScalarParameterHandle
	 * 
	 * @return
	 */
	protected String getParamValueAsString( HttpServletRequest request,
			ScalarParameterHandle parameter )
	{