demos: fix react demos again

demos/src/Examples/Book/React/index.jsx

@@ -5,6 +5,10 @@ import { content } from '../content.js'
 import './styles.scss'
 
 const MenuBar = ({ editor }) => {
+  if (!editor) {
+    return null
+  }
+
   return (
     <>
       <button

demos/src/Examples/CodeBlockLanguage/React/index.jsx

@@ -16,6 +16,10 @@ import lowlight from 'lowlight'
 import './styles.scss'
 
 const MenuBar = ({ editor }) => {
+  if (!editor) {
+    return null
+  }
+
   return (
     <button onClick={() => editor.chain().focus().toggleCodeBlock().run()} className={editor.isActive('codeBlock') ? 'is-active' : ''}>
       code block

demos/src/Examples/Default/React/index.jsx

@@ -4,6 +4,10 @@ import StarterKit from '@tiptap/starter-kit'
 import './styles.scss'
 
 const MenuBar = ({ editor }) => {
+  if (!editor) {
+    return null
+  }
+
   return (
     <>
       <button

demos/src/Examples/Formatting/React/index.jsx

@@ -6,6 +6,10 @@ import Highlight from '@tiptap/extension-highlight'
 import './styles.scss'
 
 const MenuBar = ({ editor }) => {
+  if (!editor) {
+    return null
+  }
+
   return (
     <>
       <button onClick={() => editor.chain().focus().toggleHeading({ level: 1 }).run()} className={editor.isActive('heading', { level: 1 }) ? 'is-active' : ''}>

demos/src/Examples/Savvy/React/index.jsx

@@ -11,7 +11,15 @@ import './styles.scss'
 
 export default () => {
   const editor = useEditor({
-    extensions: [Document, Paragraph, Text, Code, Typography, ColorHighlighter, SmilieReplacer],
+    extensions: [
+      Document,
+      Paragraph,
+      Text,
+      Code,
+      Typography,
+      ColorHighlighter,
+      SmilieReplacer,
+    ],
     content: `
       <p>
         → With the Typography extension, tiptap understands »what you mean« and adds correct characters to your text — it’s like a “typography nerd” on your side.

demos/src/Examples/Tables/React/index.jsx

@@ -54,6 +54,10 @@ export const tableHTML = `
 `
 
 const MenuBar = ({ editor }) => {
+  if (!editor) {
+    return null
+  }
+
   return (
     <>
       <button onClick={() => editor.chain().focus().insertTable({ rows: 3, cols: 3, withHeaderRow: true }).run()}>