Fix a crash on startup with a folder entry without entries (#14629)

`_Entries` was getting default constructed to `nullptr`. We should be careful about that. 

Adds a test too, and fixes a regression in the local tests introduced in #13763.

Closes #14557

src/cascadia/LocalTests_SettingsModel/NewTabMenuTests.cpp

@@ -0,0 +1,107 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+#include "pch.h"
+
+#include "../TerminalSettingsModel/NewTabMenuEntry.h"
+#include "../TerminalSettingsModel/FolderEntry.h"
+#include "../TerminalSettingsModel/CascadiaSettings.h"
+#include "../types/inc/colorTable.hpp"
+#include "JsonTestClass.h"
+
+#include <defaults.h>
+
+using namespace Microsoft::Console;
+using namespace winrt::Microsoft::Terminal;
+using namespace winrt::Microsoft::Terminal::Settings::Model::implementation;
+using namespace WEX::Logging;
+using namespace WEX::TestExecution;
+using namespace WEX::Common;
+
+namespace SettingsModelLocalTests
+{
+    // TODO:microsoft/terminal#3838:
+    // Unfortunately, these tests _WILL NOT_ work in our CI. We're waiting for
+    // an updated TAEF that will let us install framework packages when the test
+    // package is deployed. Until then, these tests won't deploy in CI.
+
+    class NewTabMenuTests : public JsonTestClass
+    {
+        // Use a custom AppxManifest to ensure that we can activate winrt types
+        // from our test. This property will tell taef to manually use this as
+        // the AppxManifest for this test class.
+        // This does not yet work for anything XAML-y. See TabTests.cpp for more
+        // details on that.
+        BEGIN_TEST_CLASS(NewTabMenuTests)
+            TEST_CLASS_PROPERTY(L"RunAs", L"UAP")
+            TEST_CLASS_PROPERTY(L"UAP:AppXManifest", L"TestHostAppXManifest.xml")
+        END_TEST_CLASS()
+
+        TEST_METHOD(DefaultsToRemainingProfiles);
+        TEST_METHOD(ParseEmptyFolder);
+    };
+
+    void NewTabMenuTests::DefaultsToRemainingProfiles()
+    {
+        Log::Comment(L"If the user doesn't customize the menu, put one entry for each profile");
+
+        static constexpr std::string_view settingsString{ R"json({
+        })json" };
+
+        try
+        {
+            const auto settings{ winrt::make_self<CascadiaSettings>(settingsString, DefaultJson) };
+
+            VERIFY_ARE_EQUAL(0u, settings->Warnings().Size());
+
+            const auto& entries = settings->GlobalSettings().NewTabMenu();
+            VERIFY_ARE_EQUAL(1u, entries.Size());
+            VERIFY_ARE_EQUAL(winrt::Microsoft::Terminal::Settings::Model::NewTabMenuEntryType::RemainingProfiles, entries.GetAt(0).Type());
+        }
+        catch (const SettingsException& ex)
+        {
+            auto loadError = ex.Error();
+            loadError;
+            throw ex;
+        }
+        catch (const SettingsTypedDeserializationException& e)
+        {
+            auto deserializationErrorMessage = til::u8u16(e.what());
+            Log::Comment(NoThrowString().Format(deserializationErrorMessage.c_str()));
+            throw e;
+        }
+    }
+
+    void NewTabMenuTests::ParseEmptyFolder()
+    {
+        Log::Comment(L"GH #14557 - An empty folder entry shouldn't crash");
+
+        static constexpr std::string_view settingsString{ R"json({
+            "newTabMenu": [
+                { "type": "folder" }
+            ]
+        })json" };
+
+        try
+        {
+            const auto settings{ winrt::make_self<CascadiaSettings>(settingsString, DefaultJson) };
+
+            VERIFY_ARE_EQUAL(0u, settings->Warnings().Size());
+
+            const auto& entries = settings->GlobalSettings().NewTabMenu();
+            VERIFY_ARE_EQUAL(1u, entries.Size());
+        }
+        catch (const SettingsException& ex)
+        {
+            auto loadError = ex.Error();
+            loadError;
+            throw ex;
+        }
+        catch (const SettingsTypedDeserializationException& e)
+        {
+            auto deserializationErrorMessage = til::u8u16(e.what());
+            Log::Comment(NoThrowString().Format(deserializationErrorMessage.c_str()));
+            throw e;
+        }
+    }
+}

src/cascadia/LocalTests_SettingsModel/SerializationTests.cpp

@@ -406,6 +406,12 @@ namespace SettingsModelLocalTests
             "$schema" : "https://aka.ms/terminal-profiles-schema",
             "defaultProfile": "{61c54bbd-1111-5271-96e7-009a87ff44bf}",
             "disabledProfileSources": [ "Windows.Terminal.Wsl" ],
+            "newTabMenu":
+            [
+                {
+                    "type": "remainingProfiles"
+                }
+            ],
             "profiles": {
                 "defaults": {
                     "font": {

src/cascadia/LocalTests_SettingsModel/SettingsModel.LocalTests.vcxproj

@@ -39,6 +39,7 @@
     <ClCompile Include="KeyBindingsTests.cpp" />
     <ClCompile Include="CommandTests.cpp" />
     <ClCompile Include="DeserializationTests.cpp" />
+    <ClCompile Include="NewTabMenuTests.cpp" />
     <ClCompile Include="SerializationTests.cpp" />
     <ClCompile Include="TerminalSettingsTests.cpp" />
     <ClCompile Include="ThemeTests.cpp" />

src/cascadia/TerminalSettingsModel/FolderEntry.cpp

@@ -63,6 +63,10 @@ IVector<NewTabMenuEntryModel> FolderEntry::Entries() const
     // We filter the full list of entries from JSON to just include the
     // non-empty ones.
     IVector<NewTabMenuEntryModel> result{ winrt::single_threaded_vector<NewTabMenuEntryModel>() };
+    if (_Entries == nullptr)
+    {
+        return result;
+    }
 
     for (const auto& entry : _Entries)
     {