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
}
			else
			{
				params.put( paramName, null );
			}
		}
		return params;
	}
	/**
	 * get parameter object.
	 * 
	 * @param request
	 *            HttpServletRequest
	 * @param parameter
	 *            ScalarParameterHandle
	 * 
	 * @return
	 */
	protected String getParamValueAsString( HttpServletRequest request,
			ScalarParameterHandle parameter )
	{
		String paramName = parameter.getName( );
		String paramValue = null;
		if ( ParameterAccessor.isReportParameterExist( request, paramName ) )
		{
			
			paramValue = ParameterAccessor.getReportParameter( request,
					paramName, null );
			return paramValue;
		}