Fix null reference exception on threads without suitable subjects. Bump version to 6.3.1

Author: Issung

GChan/GChan.csproj

@@ -23,9 +23,9 @@
 		<SatelliteResourceLanguages>en</SatelliteResourceLanguages>
 
 		<!-- Versioning -->
-		<Version>6.3.0</Version>
-		<AssemblyVersion>6.3.0</AssemblyVersion>
-		<FileVersion>6.3.0</FileVersion>
+		<Version>6.3.1</Version>
+		<AssemblyVersion>6.3.1</AssemblyVersion>
+		<FileVersion>6.3.1</FileVersion>
 	</PropertyGroup>
 	<PropertyGroup>
 		<ApplicationIcon>4chanIcon.ico</ApplicationIcon>

GChan/Helpers/Utils.cs

@@ -211,6 +211,7 @@ public static string CombinePathAndFilename(string directory, string filename)
         /// Remove a string of characters illegal for a folder name.<br/>
         /// Used for thread subjects if addThreadSubjectToFolder setting is enabled.
         /// </summary>
+        /// <exception cref="NullReferenceException">If <paramref name="subject"/> is null.</exception>
         public static string SanitiseSubject(string subject)
         {
             return RemoveCharactersFromString(subject, IllegalSubjectCharacters);

GChan/Models/Trackers/Sites/Thread_4Chan.cs

@@ -255,7 +255,7 @@ private void ConfigureFromUrl(string url)
 
             var result = sub ?? (nameOk ? name : null) ?? (commentOk ? comment : null);
 
-            return Utils.SanitiseSubject(result);
+            return result == null ? null : Utils.SanitiseSubject(result);
         }
     }
 }