Added method in ParseUtil that strips out every invalid XML character from a string.

Added test for ParseUtil.RemoveInvalidXmlChars() using a snippet of rss from XSeeds that was originally causing problems.

src/Jackett/Utils/ParseUtil.cs

@@ -1,9 +1,15 @@
 using System.Globalization;
+using System.Text.RegularExpressions;
 
 namespace Jackett.Utils
 {
     public static class ParseUtil
     {
+        private static readonly Regex InvalidXmlChars =
+            new Regex(
+                @"(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|[\x00-\x08\x0B\x0C\x0E-\x1F\x7F-\x9F\uFEFF\uFFFE\uFFFF]",
+                RegexOptions.Compiled);
+
         public static string NormalizeSpace(string s)
         {
             return s.Trim();
@@ -17,6 +23,11 @@ namespace Jackett.Utils
             return normalized;
         }
 
+        public static string RemoveInvalidXmlChars(string text)
+        {
+            return string.IsNullOrEmpty(text) ? "" : InvalidXmlChars.Replace(text, "");
+        }
+
         public static double CoerceDouble(string str)
         {
             return double.Parse(NormalizeNumber(str), NumberStyles.Any, CultureInfo.InvariantCulture);