fix: ai slide render initialize error (#7261)

Need add `collection.meta.initialize()` in AI slide render.
Similar codes:
b3ec3a2b3e/packages/frontend/core/src/blocksuite/presets/ai/utils/markdown-utils.ts (L177-L195)

packages/frontend/core/src/blocksuite/presets/ai/messages/slides-renderer.ts

@@ -214,6 +214,7 @@ export class AISlidesRenderer extends WithDisposable(LitElement) {
 
     const schema = new Schema().register(AffineSchemas);
     const collection = new DocCollection({ schema, id: 'SLIDES_PREVIEW' });
+    collection.meta.initialize();
     collection.start();
     const doc = collection.createDoc();