chore(ci): fix failure condition when modified files are empty

.github/workflows/cppcheck-differential.yaml

@@ -31,37 +31,33 @@ jobs:
         run: git fetch origin ${{ github.base_ref }}
         shell: bash
 
-      - name: Get changed files
-        id: changed-files
+      - name: Get changed files (existing files only)
+        id: get-changed-files
         run: |
-          git diff --name-only "origin/${{ github.base_ref }}"...HEAD > changed_files.txt
-          cat changed_files.txt
+          echo "changed-files=$(git diff --name-only "origin/${{ github.base_ref }}"...HEAD | grep -E '\.(cpp|hpp)$' | while read -r file; do [ -e "$file" ] && echo -n "$file "; done)" >> $GITHUB_OUTPUT
         shell: bash
 
       - name: Run Cppcheck on changed files
+        if: ${{ steps.get-changed-files.outputs.changed-files != '' }}
         continue-on-error: true
         id: cppcheck
         run: |
-          files=$(cat changed_files.txt | grep -E '\.(cpp|hpp)$' || true)
-          if [ -n "$files" ]; then
-            echo "Running Cppcheck on changed files: $files"
-            cppcheck --enable=all --inconclusive --check-level=exhaustive --error-exitcode=1 --suppressions-list=.cppcheck_suppressions $files 2> cppcheck-report.txt
-          else
-            echo "No C++ files changed."
-            touch cppcheck-report.txt
-          fi
+          echo "Running Cppcheck on changed files: ${{ steps.get-changed-files.outputs.changed-files }}"
+          cppcheck --enable=all --inconclusive --check-level=exhaustive --error-exitcode=1 --suppressions-list=.cppcheck_suppressions ${{ steps.get-changed-files.outputs.changed-files }} 2> cppcheck-report.txt
         shell: bash
 
       - name: Show cppcheck-report result
+        if: ${{ steps.get-changed-files.outputs.changed-files != '' }}
         run: |
           cat cppcheck-report.txt
 
       - name: Upload Cppcheck report
+        if: ${{ steps.get-changed-files.outputs.changed-files != '' }}
         uses: actions/upload-artifact@v2
         with:
           name: cppcheck-report
           path: cppcheck-report.txt
 
       - name: Fail the job if Cppcheck failed
-        if: steps.cppcheck.outcome == 'failure'
+        if: ${{ steps.get-changed-files.outputs.changed-files != '' && steps.cppcheck.outcome == 'failure' }}
         run: exit 1