Merge pull request #742 from jiripolasek/feature/MarkdownTextBlock-fix-nre-codeblock

MarkdownTextBlock: Add guard against NRE in MyCodeBlock and HtmlBlockRenderer

Author: Arlodotexe

components/MarkdownTextBlock/src/Renderers/ObjectRenderers/HtmlBlockRenderer.cs

@@ -15,14 +15,17 @@ protected override void Write(WinUIRenderer renderer, HtmlBlock obj)
         if (obj == null) throw new ArgumentNullException(nameof(obj));
 
         var stringBuilder = new StringBuilder();
-        foreach (var line in obj.Lines.Lines)
+        if (obj.Lines.Lines != null)
         {
-            var lineText = line.Slice.ToString().Trim();
-            if (String.IsNullOrWhiteSpace(lineText))
+            foreach (var line in obj.Lines.Lines)
             {
-                continue;
+                var lineText = line.Slice.ToString().Trim();
+                if (String.IsNullOrWhiteSpace(lineText))
+                {
+                    continue;
+                }
+                stringBuilder.AppendLine(lineText);
             }
-            stringBuilder.AppendLine(lineText);
         }
 
         var html = Regex.Replace(stringBuilder.ToString(), @"\t|\n|\r", "", RegexOptions.Compiled);

components/MarkdownTextBlock/src/TextElements/MyCodeBlock.cs

@@ -75,20 +75,23 @@ public MyCodeBlock(CodeBlock codeBlock, MarkdownConfig config)
         {
 #endif
 
-        foreach (var line in codeBlock.Lines.Lines)
+        if (codeBlock.Lines.Lines != null)
         {
-            var paragraph = new Paragraph();
-            var lineString = line.ToString();
-            if (!String.IsNullOrWhiteSpace(lineString))
+            foreach (var line in codeBlock.Lines.Lines)
             {
-                paragraph.Inlines.Add(new Run() { Text = lineString });
+                var paragraph = new Paragraph();
+                var lineString = line.ToString();
+                if (!String.IsNullOrWhiteSpace(lineString))
+                {
+                    paragraph.Inlines.Add(new Run() { Text = lineString });
+                }
+                richTextBlock.Blocks.Add(paragraph);
             }
-            richTextBlock.Blocks.Add(paragraph);
+
+            border.Child = richTextBlock;
+            container.Child = border;
+            _paragraph.Inlines.Add(container);
         }
-        
-        border.Child = richTextBlock;
-        container.Child = border;
-        _paragraph.Inlines.Add(container);
     }
 
     public void AddChild(IAddChild child) {}