check grub exists

tasks/kernel/fast-again.yml

+- name: check grub exists
+  become: true
+  stat:
+    path: /etc/default/grub
+  register: grub_exists
 - name: grub block
   become: true
+  when: grub_exists.stat.exists
   blockinfile:
     path: /etc/default/grub
     marker: '# {mark} MyCard Init block'
@@ -18,4 +24,4 @@
 - name: update-grub
   become: true
   shell: update-grub
-  when: grub_block_result.changed
+  when: grub_exists.stat.exists and grub_block_result.changed