Fix issue with additional empty lists breaking

src/Html2Markdown/Replacement/HtmlParser.cs

@@ -6,15 +6,25 @@ namespace Html2Markdown.Replacement;
 
 internal static partial class HtmlParser
 {
-	private static readonly Regex NoChildren = HtmlListHasNoChildren();
 
 	internal static string ReplaceLists(string html)
 	{
 		var finalHtml = html;
+		var lastRun = string.Empty;
 		while (HasNoChildLists(finalHtml))
 		{
-			var listToReplace = NoChildren.Match(finalHtml).Value;
+			var listToReplace = HtmlListHasNoChildren().Match(finalHtml).Value;
 			var formattedList = ReplaceList(listToReplace);
+
+			// an empty  signifies that the HTML is malformed in some way.
+			// so we should leave the final HTML as is
+			if (string.IsNullOrEmpty(formattedList)) {
+				finalHtml = finalHtml.Replace(listToReplace, lastRun);
+				break;
+			}
+
+			lastRun = formattedList;
+
 			finalHtml = finalHtml.Replace(listToReplace, formattedList);
 		}
 
@@ -75,7 +85,7 @@ private static bool ListOnlyHasEmptyStringsForChildren(IEnumerable<string> listI
 
 	private static bool HasNoChildLists(string html)
 	{
-		return NoChildren.Match(html).Success;
+		return HtmlListHasNoChildren().Match(html).Success;
 	}
 
 	internal static string ReplacePre(string html)

test/Html2Markdown.Test/CommonMarkSchemeConverterTest.Convert_WhenThereAreMultipleUnorderedLists_ThenReplaceWithMarkdownLists.verified.txt

@@ -0,0 +1 @@
+*   first list val

test/Html2Markdown.Test/MarkdownSchemeConverterTest.Convert_WhenThereAreMultipleUnorderedLists_ThenReplaceWithMarkdownLists.verified.txt

@@ -0,0 +1 @@
+*   first list val

test/Html2Markdown.Test/MarkdownSchemeConverterTest.cs

@@ -633,6 +633,15 @@ public Task Convert_WhenThereIsAMultilineOrderedListWithNestedParagraphsAndCodeE
 
 		return CheckConversion(html);
 	}
+
+	// See issue https://github.com/baynezy/Html2Markdown/issues/395
+	[Test]
+	public Task Convert_WhenThereAreMultipleUnorderedLists_ThenReplaceWithMarkdownLists()
+	{
+		const string html = "<ul><ul><li>first list val</li></ul></ul>";
+
+		return CheckConversion(html);
+	}
 
 	#endregion