Fix tests

Author: amcasey

src/Shared/CertificateGeneration/CertificateManager.cs

@@ -314,7 +314,7 @@ public EnsureCertificateResult EnsureAspNetCoreHttpsDevelopmentCertificate(
                 // If the user specified a non-existent directory, we don't want to be responsible
                 // for setting the permissions appropriately, so we'll bail.
                 var exportDir = Path.GetDirectoryName(path);
-                if (!Directory.Exists(exportDir))
+                if (!string.IsNullOrEmpty(exportDir) && !Directory.Exists(exportDir))
                 {
                     throw new InvalidOperationException($"The directory '{exportDir}' does not exist.");
                 }