Compare to 0 to get the desired result

src/Umbraco.Web.UI.Client/src/common/services/tree.service.js

@@ -166,8 +166,8 @@ function treeService($q, treeResource, iconHelper, notificationsService, eventsS
                 angular.isArray(Umbraco.Sys.ServerVariables.umbracoPlugins.trees)) {
 
                 var found = _.find(Umbraco.Sys.ServerVariables.umbracoPlugins.trees, function (item) {
-                    // localeCompare returns 0 when strings are equal so we need to add one to make it true.
-                    return item.alias.localeCompare(treeAlias, undefined, { ignorePunctuation: true }) + 1;
+                    // localeCompare returns 0 when strings are equal, so return false if there's no match
+                    return item.alias.localeCompare(treeAlias, undefined, { ignorePunctuation: true }) !== 0;
                 });
 
                 return found ? found.packageFolder : undefined;