Fixed CodeQL compile issue + a warning

Duplicati/GUI/Duplicati.GUI.TrayIcon/HttpServerConnection.cs

@@ -148,7 +148,7 @@ namespace Duplicati.GUI.TrayIcon
 
             var acceptedCertificates = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
             if (!string.IsNullOrWhiteSpace(acceptedHostCertificate))
-                acceptedCertificates.UnionWith(acceptedHostCertificate.Split([',', ';'],
+                acceptedCertificates.UnionWith(acceptedHostCertificate.Split(new char[] { ',', ';' },
                     StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries));
 
             HTTPCLIENT = new(new HttpClientHandler

Duplicati/Library/Backend/OpenStack/OpenStackStorage.cs

@@ -418,7 +418,7 @@ public class OpenStackStorage : IStreamingBackend
                 yield break;
 
             // Prepare next listing entry
-            url = plainurl + $"&marker={Uri.UrlEncode(items.Last().name)}";
+            url = plainurl + $"&marker={Uri.UrlEncode(items.Last().name ?? "")}";
         }
     }