do not throw warn if content is null

packages/tiptap/src/Editor.js

@@ -177,6 +177,10 @@ export default class Editor {
   }
 
   createDocument(content) {
+    if (content === null) {
+      return this.schema.nodeFromJSON(this.options.emptyDocument)
+    }
+
     if (typeof content === 'object') {
       try {
         return this.schema.nodeFromJSON(content)

packages/tiptap/test/Editor.spec.js

@@ -25,6 +25,14 @@ test('create editor', () => {
   expect(editor).toBeDefined()
 })
 
+test('check empty content (null)', () => {
+  const editor = new Editor({
+    content: null,
+  })
+
+  expect(editor.getHTML()).toEqual('<p></p>')
+})
+
 test('check invalid content (JSON)', () => {
   const editor = new Editor({
     content: { thisIsNotAValidDocument: true },