GitHub Actions workflow fails on PRs with no Python files

[tripti-gupta700]

Label: bug, level: advanced

Description:
The PR validation workflow errors out when a contributor submits
a documentation-only PR (no .py files). pyflakes throws an error
on empty input instead of skipping gracefully.

Task:
Add a conditional check — only run pyflakes if .py files exist in the PR diff.

File: .github/workflows/pr-check.yml

[asiyamujawar]

I'd like to work on this issue. Could you assign it to me?