Freemarker sample template fixes

Author: stefan-ka

org.contextmapper.dsl.ui/samples/freemarker/markdown-templates/FullReportTemplate.md.ftl

@@ -6,7 +6,7 @@
 Model Report for '${fileName}' 
 ==============================
 
-*Note:* This domain model is part of project '${projectName}'.
+*Note:* This domain model is part of project '${projectName!"undefined"}'.
 
 <#if domains?has_content>
     Analysis Part<#lt>

org.contextmapper.dsl.ui/samples/freemarker/markdown-templates/common/header.md.ftl

@@ -1,7 +1,7 @@
 ---
 title: Report generated from '${fileName}'
-project: ${projectName}
-author: ${userName}
-date: ${timeStamp}, Context Mapper version ${contextMapperVersion}
-copyright: The authors, 2020. All rights reserved.
+project: ${projectName!"undefined"}
+author: ${userName!"undefined"}
+date: ${timeStamp!"undefined"}, Context Mapper version ${contextMapperVersion!"undefined"}
+copyright: The authors, 2020-2023. All rights reserved.
 ---