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
if ( parameterList == null || this.parametersAsString == null )
			return params;
		for ( Iterator iter = parameterList.iterator( ); iter.hasNext( ); )
		{
			ScalarParameterHandle parameter = null;
			Object parameterObj = iter.next( );
			if ( parameterObj instanceof ScalarParameterHandle )
			{
				parameter = (ScalarParameterHandle) parameterObj;
			}
			
			if ( parameter == null )
				continue;
			String paramName = parameter.getName( );
			Object paramValueObj = this.parametersAsString.get( paramName );
			if ( paramValueObj != null )
			{
				try
				{
					String format = ParameterAccessor.getFormat( request,
							paramName );
					if ( format != null && format.length( ) > 0 )
					{
						
						paramValueObj = ParameterValidationUtil.validate(
								parameter.getDataType( ), format, paramValueObj
										.toString( ), locale );
					}
					else
					{