I think there is a weird bug caused by the latest update
When I am updating a page and type rendered="", an exception is always thrown. It tells me to look for more info in the ActivityLog.xml on the exception
This is what I found
<entry>
<record>379</record>
<time>2017/12/27 18:53:31.286</time>
<type>Information</type>
<source>Web Editor</source>
<description>System.NullReferenceException: Object reference not set to an instance of an object.
 at Microsoft.Html.Editor.QuoteCompletion.CreateProvisionalText(ITextView textView, Int32 position, Char eatNextQuote)
 at Microsoft.Html.Editor.QuoteCompletion.CompleteQuotes(ITextView textView, HtmlEditorTree tree, Int32 position, Char typedChar)
 at Microsoft.Html.Editor.HtmlTypingCommandHandler.HandleCompletion(Char typedChar)
 at Microsoft.Html.Editor.HtmlTypingCommandHandler.PostProcessInvoke(CommandResult result, Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Web.Editor.Controller.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Web.Editor.ViewController.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Html.Editor.HtmlMainController.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.VisualStudio.Html.Interop.CommandTargetToOleShim.Exec(Guid& guidCommandGroup, UInt32 commandID, UInt32 commandExecOpt, IntPtr variantIn, IntPtr variantOut)</description>
</entry>
<entry>
<record>380</record>
<time>2017/12/27 18:53:31.295</time>
<type>Error</type>
<source>Editor or Editor Extension</source>
<description>System.NullReferenceException: Object reference not set to an instance of an object.
 at Microsoft.Html.Editor.QuoteCompletion.CreateProvisionalText(ITextView textView, Int32 position, Char eatNextQuote)
 at Microsoft.Html.Editor.QuoteCompletion.CompleteQuotes(ITextView textView, HtmlEditorTree tree, Int32 position, Char typedChar)
 at Microsoft.Html.Editor.HtmlTypingCommandHandler.HandleCompletion(Char typedChar)
 at Microsoft.Html.Editor.HtmlTypingCommandHandler.PostProcessInvoke(CommandResult result, Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Web.Editor.Controller.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Web.Editor.ViewController.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.Html.Editor.HtmlMainController.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg)
 at Microsoft.VisualStudio.Html.Interop.CommandTargetToOleShim.Exec(Guid& guidCommandGroup, UInt32 commandID, UInt32 commandExecOpt, IntPtr variantIn, IntPtr variantOut)
 at Microsoft.VisualStudio.Editor.Implementation.CommandChainNode.InnerExec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut)
 at Microsoft.VisualStudio.Editor.Implementation.SimpleTextViewWindow.Exec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut)
 at Microsoft.VisualStudio.Editor.Implementation.VsKeyboardFilter.SendCommand(Guid cmdGroup, UInt32 cmdID, Object inParam)
 at Microsoft.VisualStudio.Editor.Implementation.VsKeyboardFilter.TextInput(TextCompositionEventArgs args)
 at Microsoft.VisualStudio.Text.Editor.Implementation.KeyProcessorDispatcher.<DispatchTextInputEvents>b__0(KeyProcessor p, TextCompositionEventArgs args)
 at Microsoft.VisualStudio.Text.Editor.Implementation.KeyProcessorDispatcher.<>c__DisplayClass1e`1.<Dispatch>b__1a()
 at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.CallExtensionPoint(Object errorSource, Action call)</description>
</entry>