Fix allow adding bookmark folders

Auditors: @darkdh

Fix #7229

I decided to stick with needing a fodlerId to avoid future bugs with infinite recursion

app/renderer/components/addEditBookmarkHanger.js

@@ -54,7 +54,9 @@ class AddEditBookmarkHanger extends ImmutableComponent {
       : 'bookmarkAdded'
   }
   get isFolder () {
-    return siteUtil.isFolder(this.props.currentDetail)
+    // Fake a folderId property so that the bookmark is considered a bookmark folder.
+    // This is ImmutableJS so it doesn't actually set a value, it just returns a new one.
+    return siteUtil.isFolder(this.props.currentDetail.set('folderId', 0))
   }
   setDefaultFocus () {
     this.bookmarkName.select()

js/state/siteUtil.js

@@ -527,7 +527,7 @@ module.exports.isHistoryEntry = function (siteDetail) {
     if (siteDetail.get('location').startsWith('about:')) {
       return false
     }
-    return !!siteDetail.get('lastAccessedTime') && !module.exports.isFolder(siteDetail)
+    return !!siteDetail.get('lastAccessedTime') && !isBookmarkFolder(siteDetail.get('tags'))
   }
   return false
 }

test/unit/state/siteUtilTest.js

@@ -954,7 +954,8 @@ describe('siteUtil', function () {
         tags: [siteTags.BOOKMARK]
       })
       const siteDetail2 = Immutable.fromJS({
-        tags: [siteTags.BOOKMARK_FOLDER]
+        tags: [siteTags.BOOKMARK_FOLDER],
+        folderId: 1
       })
       assert.equal(siteUtil.isEquivalent(siteDetail1, siteDetail2), false)
     })
@@ -996,12 +997,19 @@ describe('siteUtil', function () {
   })
 
   describe('isFolder', function () {
-    it('returns true if the input is a siteDetail and has a `BOOKMARK_FOLDER` tag', function () {
+    it('returns true if the input is a siteDetail and has a `BOOKMARK_FOLDER` tag and a folder ID', function () {
       const siteDetail = Immutable.fromJS({
-        tags: [siteTags.BOOKMARK_FOLDER]
+        tags: [siteTags.BOOKMARK_FOLDER],
+        folderId: 1
       })
       assert.equal(siteUtil.isFolder(siteDetail), true)
     })
+    it('returns false if the input does not have a folderId', function () {
+      const siteDetail = Immutable.fromJS({
+        tags: [siteTags.BOOKMARK_FOLDER]
+      })
+      assert.equal(siteUtil.isFolder(siteDetail), false)
+    })
     it('returns false if the input does not have a `BOOKMARK_FOLDER` tag', function () {
       const siteDetail = Immutable.fromJS({
         tags: [siteTags.BOOKMARK]