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
assert attrBean != null;
		
		String reportDesignName = attrBean.getReportDesignName( );
		
		String configFileName = ParameterAccessor
				.getConfigFileName( reportDesignName );
		if ( configFileName == null )
		{
			handleUpdate( );
			return;
		}
		
		SessionHandle sessionHandle = DesignEngine.newSession( ULocale.US );
		File configFile = new File( configFileName );
		
		if ( configFile != null && configFile.exists( ) && configFile.isFile( ) )
		{
			configFile.delete( );
		}
		
		ReportDesignHandle handle = sessionHandle.createDesign( );
		
		String displayTextParam = null;
		Oprand[] op = this.operation.getOprand( );
		if ( op != null )
		{
			for ( int i = 0; i < op.length; i++ )
			{
				ConfigVariable configVar = new ConfigVariable( );
				String paramName = op[i].getName( );