fix oqtane#4795 - ensure deterministic ordering of file parts when me…

…rging files after upload (credit @HQuast)

Oqtane.Server/Controllers/FileController.cs

@@ -517,7 +517,7 @@ private async Task<string> MergeFile(string folder, string filename)
                 bool success = true;
                 using (var stream = new FileStream(Path.Combine(folder, filename + ".tmp"), FileMode.Create))
                 {
-                    foreach (string filepart in fileparts)
+                    foreach (string filepart in fileparts.Order())
                     {
                         try
                         {