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
File file = new File( this.reportDesignName );
				if ( file.exists( ) )
				{
					reportRunnable = ReportEngineService.getInstance( )
							.openReportDesign( this.reportDesignName );
				}
				else
				{
					
					this.reportDesignName = ParameterAccessor.getParameter(
							request, ParameterAccessor.PARAM_REPORT );
					InputStream is = request.getSession( ).getServletContext( )
							.getResourceAsStream( this.reportDesignName );
					reportRunnable = ReportEngineService.getInstance( )
							.openReportDesign( is );
				}
			}
			catch ( EngineException e )
			{
				this.exception = e;
			}
		}
		if ( reportRunnable != null )
		{
			design = new BirtViewerReportDesignHandle(
					IViewerReportDesignHandle.RPT_RUNNABLE_OBJECT,
					reportRunnable );
		}
		else