Add guards for possible null value in cm.state.vim introduced by codemirror-vim

Author: firai

src/codemirrorCommands.ts

@@ -99,6 +99,7 @@ export class VimEditorManager {
         // we override `hasFocus` handler to ensure it is taken into account.
         const cm = getCM(view)!;
         cm.on('vim-mode-change', () => {
+          if (!cm.state.vim) return;
           editor.host.dataset.jpVimModeName = cm.state.vim.mode;
         });
         mirrorEditor.hasFocus = () => {

src/labCommands.ts

@@ -180,6 +180,7 @@ export function addNotebookCommands(
               return;
             }
             const vim = cm.state.vim;
+            if (!vim) return;
 
             // Get the current editor state
             if (