U4-9326 Removing a master template from a Template does not update the Template's path correctly

src/Umbraco.Core/Persistence/Repositories/TemplateRepository.cs

@@ -241,7 +241,12 @@ namespace Umbraco.Core.Persistence.Repositories
                 {
                     entity.Path = string.Concat(parent.Path, ",", entity.Id);
                 }
-
+                else
+                {
+                    //this means that the master template has been removed, so we need to reset the template's
+                    //path to be at the root
+                    entity.Path = string.Concat("-1,", entity.Id);
+                }
             }
 
             //Get TemplateDto from db to get the Primary key of the entity

src/Umbraco.Tests/Persistence/Repositories/TemplateRepositoryTest.cs

@@ -707,6 +707,35 @@ namespace Umbraco.Tests.Persistence.Repositories
             }
         }
 
+        [Test]
+        public void Path_Is_Set_Correctly_On_Update_With_Master_Template_Removal()
+        {
+            // Arrange
+            var provider = new PetaPocoUnitOfWorkProvider(Logger);
+            var unitOfWork = provider.GetUnitOfWork();
+            using (var repository = CreateRepository(unitOfWork))
+            {
+                var parent = new Template("parent", "parent");
+                var child1 = new Template("child1", "child1");
+
+                child1.MasterTemplateAlias = parent.Alias;
+                child1.MasterTemplateId = new Lazy<int>(() => parent.Id);               
+
+                repository.AddOrUpdate(parent);
+                repository.AddOrUpdate(child1);
+                unitOfWork.Commit();
+
+                //Act
+                child1.SetMasterTemplate(null);
+                repository.AddOrUpdate(child1);
+                unitOfWork.Commit();
+
+                //Assert
+                Assert.AreEqual(string.Format("-1,{0}", child1.Id), child1.Path);
+
+            }
+        }
+
 
         [TearDown]
         public override void TearDown()