Fixed accent color not updating in front-end preview

refs https://github.com/TryGhost/Ghost/pull/12717

- preview data is set on `options.data.site` so we need to read from that rather than directly from the settings cache

core/frontend/helpers/ghost_head.js

@@ -173,8 +173,8 @@ module.exports = function ghost_head(options) { // eslint-disable-line camelcase
                 }
             }
 
-            if (settingsCache.get('accent_color')) {
+            if (options.data.site.accent_color) {
-                const accentColor = escapeExpression(settingsCache.get('accent_color'));
+                const accentColor = escapeExpression(options.data.site.accent_color);
                 const styleTag = `<style>:root {--ghost-accent-color: ${accentColor};}</style>`;
                 const existingScriptIndex = _.findLastIndex(head, str => str.match(/<\/(style|script)>/));
 

test/unit/helpers/ghost_head_spec.js

@@ -1555,13 +1555,18 @@ describe('{{ghost_head}} helper', function () {
 
     describe('accent_color', function () {
         it('includes style tag when set', function (done) {
-            settingsCache.get.withArgs('accent_color').returns('#123456');
-
             const renderObject = {
                 post: posts[1]
             };
 
+            const templateOptions = {
+                site: {
+                    accent_color: '#123456'
+                }
+            };
+
             helpers.ghost_head(testUtils.createHbsResponse({
+                templateOptions,
                 renderObject: renderObject,
                 locals: {
                     relativeUrl: '/post/',
@@ -1576,13 +1581,18 @@ describe('{{ghost_head}} helper', function () {
         });
 
         it('does not include style tag when not set', function (done) {
-            settingsCache.get.withArgs('accent_color').returns(null);
-
             const renderObject = {
                 post: posts[1]
             };
 
+            const templateOptions = {
+                site: {
+                    accent_color: null
+                }
+            };
+
             helpers.ghost_head(testUtils.createHbsResponse({
+                templateOptions,
                 renderObject: renderObject,
                 locals: {
                     relativeUrl: '/post/',
@@ -1597,13 +1607,18 @@ describe('{{ghost_head}} helper', function () {
         });
 
         it('attaches style tag to existing script/style tag', function (done) {
-            settingsCache.get.withArgs('accent_color').returns('#123456');
-
             const renderObject = {
                 post: posts[1]
             };
 
+            const templateOptions = {
+                site: {
+                    accent_color: '#123456'
+                }
+            };
+
             helpers.ghost_head(testUtils.createHbsResponse({
+                templateOptions,
                 renderObject: renderObject,
                 locals: {
                     relativeUrl: '/post/',