Fixed TypeError when editor is focussed when not loaded

fix https://linear.app/tryghost/issue/SLO-162/typeerror-thiseditorapi-is-null

- if the editor does not load for some reason (network issue), and the
  editor area is clicked, we throw an error because we don't protect
  against a null `editorAPI`
- this adds that check

ghost/admin/app/components/gh-koenig-editor-lexical.js

@@ -236,7 +236,7 @@ export default class GhKoenigEditorLexical extends Component {
     // otherwise the browser will defocus the editor and the cursor will disappear
     @action
     focusEditor(event) {
-        if (!this.skipFocusEditor && event.target.classList.contains('gh-koenig-editor-pane')) {
+        if (!this.skipFocusEditor && event.target.classList.contains('gh-koenig-editor-pane') && this.editorAPI) {
             let editorCanvas = this.editorAPI.editorInstance.getRootElement();
             let {bottom} = editorCanvas.getBoundingClientRect();