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/service/actionhandler/BirtCacheParameterActionHandler.java
String paramValue = op[i].getValue( );
				ScalarParameterHandle parameter = null;
				
				if ( paramName
						.equalsIgnoreCase( ParameterAccessor.PARAM_ISNULL )
						&& paramValue != null )
				{
					parameter = (ScalarParameterHandle) attrBean
							.findParameter( paramValue );
					if ( parameter != null )
					{
						
						configVar.setName( ParameterAccessor.PARAM_ISNULL );
						configVar.setValue( paramValue
								+ "_" + parameter.getID( ) ); 
						handle.addConfigVariable( configVar );
					}
					continue;
				}
				else if ( ( displayTextParam = ParameterAccessor
						.isDisplayText( paramName ) ) != null )
				{
					parameter = (ScalarParameterHandle) attrBean
							.findParameter( displayTextParam );
					if ( parameter != null )
					{
						
						configVar
								.setName( paramName + "_" + parameter.getID( ) ); 
						configVar.setValue( paramValue );