Use Umbraco Path instead of constant

src/Umbraco.Core/Sync/ApplicationUrlHelper.cs

@@ -112,12 +112,25 @@ namespace Umbraco.Core.Sync
         /// <returns></returns>
         public static Uri GetApplicationUriUncached(
             HttpRequestBase request,
-            IUmbracoSettingsSection umbracoSettingsSection)
+            IUmbracoSettingsSection umbracoSettingsSection,
+            IGlobalSettings globalSettings)
         {
             var settingUrl = umbracoSettingsSection.WebRouting.UmbracoApplicationUrl;
-            return string.IsNullOrEmpty(settingUrl)
-                ? new Uri(request.Url, IOHelper.ResolveUrl(SystemDirectories.Umbraco))
-                : new Uri(settingUrl);
+
+
+            if (string.IsNullOrEmpty(settingUrl))
+            {
+                if (!Uri.TryCreate(request.Url, VirtualPathUtility.ToAbsolute(globalSettings.Path), out var result))
+                {
+                    throw new InvalidOperationException(
+                        $"Could not create an url from {request.Url} and {globalSettings.Path}");
+                }
+                return result;
+            }
+            else
+            {
+                return new Uri(settingUrl);
+            }
         }
     }
 }

src/Umbraco.Web/Editors/AuthenticationController.cs

@@ -566,7 +566,7 @@ namespace Umbraco.Web.Editors
                 });
 
             // Construct full URL using configured application URL (which will fall back to current request)
-            var applicationUri = ApplicationUrlHelper.GetApplicationUriUncached(http.Request, _umbracoSettingsSection);
+            var applicationUri = ApplicationUrlHelper.GetApplicationUriUncached(http.Request, _umbracoSettingsSection, GlobalSettings);
             var callbackUri = new Uri(applicationUri, action);
             return callbackUri.ToString();
         }

src/Umbraco.Web/Editors/UsersController.cs

@@ -540,7 +540,7 @@ namespace Umbraco.Web.Editors
                 });
 
             // Construct full URL will use the value in settings if specified, otherwise will use the current request URL
-            var requestUrl = ApplicationUrlHelper.GetApplicationUriUncached(http.Request, _umbracoSettingsSection);
+            var requestUrl = ApplicationUrlHelper.GetApplicationUriUncached(http.Request, _umbracoSettingsSection, GlobalSettings);
             var inviteUri = new Uri(requestUrl, action);
 
             var emailSubject = Services.TextService.Localize("user", "inviteEmailCopySubject",