fix a problem when parsing with ---\n---\n

Author: takano03

Microsoft.Toolkit.Parsers/Markdown/Blocks/YamlHeaderBlock.cs

@@ -78,7 +78,6 @@ internal static YamlHeaderBlock Parse(string markdown, int start, int end, out i
                 else if (end - pos >= 3 && markdown.Substring(pos, 3) == "---")
                 {
                     lockedFinalUnderline = true;
-                    realEndIndex = pos + 3;
                     break;
                 }
                 else if (startOfNextLine == pos + 1)
@@ -134,6 +133,7 @@ internal static YamlHeaderBlock Parse(string markdown, int start, int end, out i
                 return null;
             }
 
+            realEndIndex = pos + 3;
             return result;
         }
 

UnitTests/UnitTests.UWP/Markdown/Parse/HorizontalRuleTests.cs

@@ -107,5 +107,18 @@ public void HorizontalRule_Negative_FourStars()
                 new ParagraphBlock().AddChildren(
                     new TextRunInline { Text = "before ** after" }));
         }
+
+        [TestMethod]
+        [TestCategory("Parse - block")]
+        public void HorizontalRule_DoubleLine()
+        {
+            AssertEqual(
+                CollapseWhitespace(@"
+                ---
+                ---
+                "),
+                new HorizontalRuleBlock(),
+                new HorizontalRuleBlock());
+        }
     }
 }