fix(ci): diff_check should not fail when all files are filtered (#3658

)

This happens when only `*.md` files are changed.

.github/workflows/skip-ci.yml

@@ -28,7 +28,7 @@ jobs:
 
  skipList=(".github/CODEOWNERS" ".prettierignore")
  # Ignores changelog.md, readme.md,...
- fileChangesArray=($(git diff --name-only origin/${{ github.base_ref }}..origin/${{ github.head_ref }} | grep -v '\.md$'))
+ fileChangesArray=($(git diff --name-only origin/${{ github.base_ref }}..origin/${{ github.head_ref }} | grep -v '\.md$' || true))
  printf '%s\n' "${fileChangesArray[@]}"
  for item in "${fileChangesArray[@]}"
  do