Fix a bug when li is empty #151

Author: onizet

src/Html2OpenXml/Expressions/Numbering/ListExpression.cs

@@ -78,6 +78,7 @@ public override IEnumerable<OpenXmlElement> Interpret(ParsingContext context)
         {
             var expression = new BlockElementExpression(liNode);
             var childElements = expression.Interpret(context);
+            if (!childElements.Any()) continue;
             Paragraph p = (Paragraph) childElements.First();
 
             p.ParagraphProperties ??= new();

test/HtmlToOpenXml.Tests/NumberingTests.cs

@@ -131,6 +131,16 @@ public void EmptyList_ShouldBeIgnored()
             }
         }
 
+        [Test(Description = "Empty list item should not be registred")]
+        public void EmptyLiElement_ShouldBeIgnored()
+        {
+            var elements = converter.Parse(@"<ul>
+                <li>not empty</li>
+                <li></li>
+                </ul>");
+            Assert.That(elements, Has.Count.EqualTo(1));
+        }
+
         [Test(Description = "Increment instanceId based on existing lists")]
         public void WithExistingNumbering_ReturnsUniqueInstanceId()
         {