Merge remote-tracking branch 'origin/dev-v7' into dev-v8

# Conflicts:
#	.gitignore
#	build/UmbracoVersion.txt
#	src/Umbraco.Core/Configuration/UmbracoVersion.cs
#	src/Umbraco.Core/Persistence/Migrations/Upgrades/TargetVersionSeven/UpdateRelatedLinksData.cs
#	src/Umbraco.Core/Services/DataTypeService.cs
#	src/Umbraco.Core/Xml/XmlHelper.cs
#	src/Umbraco.Tests/Routing/UrlRoutingTestBase.cs
#	src/Umbraco.Tests/TestHelpers/BaseDatabaseFactoryTest.cs
#	src/Umbraco.Tests/TestHelpers/BaseUmbracoApplicationTest.cs
#	src/Umbraco.Web.UI/Umbraco.Web.UI.csproj
#	src/Umbraco.Web.UI/config/ClientDependency.config
#	src/Umbraco.Web.UI/umbraco/config/lang/da.xml
#	src/Umbraco.Web/PropertyEditors/GridPropertyEditor.cs
#	src/Umbraco.Web/PropertyEditors/ImageCropperPropertyEditor.cs
#	src/Umbraco.Web/PropertyEditors/LabelPropertyEditor.cs
#	src/Umbraco.Web/PropertyEditors/MultipleMediaPickerPropertyEditor.cs
#	src/Umbraco.Web/Routing/ContentFinderByLegacy404.cs
#	src/Umbraco.Web/Routing/NotFoundHandlerHelper.cs
#	src/Umbraco.Web/Umbraco.Web.csproj
#	src/Umbraco.Web/umbraco.presentation/content.cs
#	src/Umbraco.Web/umbraco.presentation/umbraco/create/DLRScriptingTasks.cs
#	src/Umbraco.Web/umbraco.presentation/umbraco/create/language.ascx.cs
#	src/Umbraco.Web/umbraco.presentation/umbraco/developer/Python/editPython.aspx.cs
#	src/Umbraco.Web/umbraco.presentation/umbraco/dialogs/sendToTranslation.aspx.cs
#	src/umbraco.cms/businesslogic/Packager/Installer.cs
#	src/umbraco.cms/businesslogic/translation/Translation.cs

src/Umbraco.Web/Scheduling/BackgroundTaskRunner.cs

@@ -305,7 +305,9 @@ namespace Umbraco.Web.Scheduling
 
             // tasks in the queue will be executed...
             if (wait == false) return;
-            _runningTask.Wait(); // wait for whatever is running to end...
+
+            if (_runningTask != null)
+                _runningTask.Wait(); // wait for whatever is running to end...
         }
 
         /// <summary>