Bug 153412 Change parameter type will cause preview fail
Description: Change parameter type will cause preview fail Steps to reproduce: 1. New a report paramter, string, text-box, default value is abc. 2. Drag the parameter to Layout and preview. 3. Change the parameter's type to integer, list-box, add a value 1 4. Preview Expected result: No errors. Actual result: The value "abc" is invalid with the type "integer".
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
SessionHandle sessionHandle = DesignEngine.newSession( ULocale.US );
		ReportDesignHandle handle = null;
		try
		{
			
			handle = sessionHandle.openDesign( reportConfigName );
			
			if ( handle != null )
			{
				String displayTextParam = null;
				Iterator configVars = handle.configVariablesIterator( );
				while ( configVars != null && configVars.hasNext( ) )
				{
					ConfigVariableHandle configVar = (ConfigVariableHandle) configVars
							.next( );
					if ( configVar != null && configVar.getName( ) != null )
					{
						String paramName = configVar.getName( );
						String paramValue = configVar.getValue( );
						
						if ( paramName
								.equalsIgnoreCase( ParameterAccessor.PARAM_ISNULL )
								&& paramValue != null )
						{
							String nullParamName = getParameterName( paramValue );
							if ( nullParamName != null )
								this.configMap.put( nullParamName, null );
							continue;
						}