Explain why not to normalize link title into empty strings

Author: Akarinnnnn

src/Markdig/Helpers/LinkHelper.cs

@@ -411,7 +411,7 @@ public static bool TryParseInlineLink(ref StringSlice text, out string? link, ou
         {
             // Skip ')'
             text.SkipChar();
-            // not to normalize nulls
+            // not to normalize nulls into empty strings, since LinkInline.Title property is nullable.
         }
 
         return isValid;
@@ -1565,4 +1565,4 @@ public static bool TryParseLabelTrivia<T>(ref T lines, bool allowEmpty, out stri
         label = buffer.ToString();
         return true;
     }
-}
+}