Fix for empty Authorization Header

src/Microsoft.AspNetCore.SystemWebAdapters.CoreServices/Authentication/RemoteAppAuthenticationService.cs

@@ -113,17 +113,24 @@ internal static void AddHeaders(IEnumerable<string> headersToForward, HttpReques
 
         foreach (var headerName in headerNames)
         {
-            // Workaround for an issue identified by https://github.com/dotnet/systemweb-adapters/issues/228.
-            // HttpClient wrongly uses comma (",") instead of semi-colon (";") as a separator for Cookie headers.
-            // To mitigate this, we concatenate them manually and put them back as a single header value.
-            // This workaround can be removed once we target .NET 7+ as Kestrel is fixed there.
+            var originalHeaders = originalRequest.Headers[headerName].Where(x => !string.IsNullOrEmpty(x)).ToArray();
+
+            if (originalHeaders.Length == 0)
+            {
+                continue;
+            }
+
+            // Workaround for an issue identified by https://github.com/dotnet/systemweb-adapters/issues/228.
+            // HttpClient wrongly uses comma (",") instead of semi-colon (";") as a separator for Cookie headers.
+            // To mitigate this, we concatenate them manually and put them back as a single header value.
+            // This workaround can be removed once we target .NET 7+ as Kestrel is fixed there.
             if (string.Equals(headerName, HeaderNames.Cookie, StringComparison.OrdinalIgnoreCase))
             {
-                authRequest.Headers.Add(headerName, string.Join("; ", originalRequest.Headers[headerName].ToArray()));
+                authRequest.Headers.Add(headerName, string.Join("; ", originalHeaders));
                 continue;
             }
 
-            authRequest.Headers.Add(headerName, originalRequest.Headers[headerName].ToArray());
+            authRequest.Headers.Add(headerName, originalHeaders); 
         }
     }