🐛 Fixed editor crashing with unknown cards in mobiledoc (#16430)

refs TryGhost/Team#2702

- adds a default handler for unknown cards: 
- logs a warning message to the console 
- removes the card from the mobiledoc

ghost/admin/lib/koenig-editor/addon/components/koenig-editor.js

@@ -189,7 +189,12 @@ export default class KoenigEditor extends Component {
             spellcheck: this.spellcheck,
             autofocus: this.autofocus,
             atoms,
-            cards
+            cards,
+            unknownCardHandler: ({env}) => {
+                console.warn(`Unknown card encountered: ${env.name}`); //eslint-disable-line
+                
+                env.remove();
+            }
         }, options);
     }
 
@@ -807,7 +812,7 @@ export default class KoenigEditor extends Component {
         // refresh drag/drop
         // TODO: can be made more performant by only refreshing when droppable
         // order changes or when sections are added/removed
-        this._cardDragDropContainer.refresh();
+        this._cardDragDropContainer?.refresh();
     }
 
     cursorDidChange(editor) {

ghost/admin/tests/acceptance/editor-test.js

@@ -632,5 +632,75 @@ describe('Acceptance: Editor', function () {
 
             // no expects, will throw with an error and fail when it hits the bug
         });
+
+        // https://github.com/TryGhost/Team/issues/2702
+        it('removes unknown cards instead of crashing', async function () {
+            let post = this.server.create('post', {authors: [author], status: 'published', title: 'Title', mobiledoc: JSON.stringify({
+                version: '0.3.1',
+                atoms: [],
+                cards: [
+                    [
+                        'asdfadsfasdfasdfadsf',
+                        {
+                            cardWidth: 'wide',
+                            startingPosition: 50,
+                            caption: 'Salmon On The Grill: BEFORE / AFTER'
+                        }
+                    ]
+                ],
+                markups: [],
+                sections: [
+                    [
+                        1,
+                        'p',
+                        [
+                            [
+                                0,
+                                [],
+                                0,
+                                'Paragraph 1'
+                            ]
+                        ]
+                    ],
+                    [
+                        10,
+                        0
+                    ]
+                ],
+                ghostVersion: '4.0'
+            })});
+
+            await visit(`/editor/post/${post.id}`);
+
+            expect(currentURL(), 'currentURL').to.equal(`/editor/post/${post.id}`);
+
+            // Make an edit and save
+            await fillIn('[data-test-editor-title-input]', 'Title 2');
+            await click('[data-test-button="publish-save"]');
+
+            // Check that the unknown card has been removed
+            expect(
+                this.server.db.posts.find(post.id).mobiledoc,
+                'removed unknown card from mobiledoc'
+            ).to.deep.equal(JSON.stringify({version: '0.3.1',
+                atoms: [],
+                cards: [],
+                markups: [],
+                sections: [
+                    [
+                        1,
+                        'p',
+                        [
+                            [
+                                0,
+                                [],
+                                0,
+                                'Paragraph 1'
+                            ]
+                        ]
+                    ]
+                ],
+                ghostVersion: '4.0'}));
+        });
     });
 });