Add warning for including empty segments or files in optional mode

docs/userGuide/syntax/siteNavigationMenus.md

@@ -34,7 +34,10 @@ You can **append the `:expanded:` to a <tooltip content="a menu item with sub me
 
 </div>
 
-<div id="examples"></div>
+<div id="examples" class="d-none">
+
+You can see an example of a Site Navigation Menu ==on the left side== of <a target="_blank" href="{{ baseUrl }}/userGuide/formattingContents.html">this page</a>.
+</div>
 
 <div id="short" class="d-none">
 

packages/core/src/html/includePanelProcessor.ts

@@ -228,6 +228,12 @@ export function processInclude(node: MbNode, context: Context, pageSources: Page
     childContext,
   } = variableProcessor.renderIncludeFile(actualFilePath, pageSources, node, context, filePath);
 
+  if (nunjucksProcessed.trim() === '') {
+    const warning = `Empty file included in ${context.cwf}:\n`
+        + `File: ${actualFilePath} is empty or contains only whitespace`;
+    logger.warn(warning);
+  }
+
   let actualContent = nunjucksProcessed;
   if (fsUtil.isMarkdownFileExt(path.extname(actualFilePath))) {
     actualContent = isInline
@@ -269,6 +275,10 @@ export function processInclude(node: MbNode, context: Context, pageSources: Page
       logger.error(error);
 
       actualContent = cheerio.html(createErrorNode(node, error));
+    } else if (actualContentOrNull === '') {
+      const warning = `Empty reference in ${context.cwf}:\n`
+          + `Segment '${hash}' in file: ${actualFilePath} is empty`;
+      logger.warn(warning);
     }
   }