Configure warnings for file-not-found.

Author: esilvia

.github/workflows/pdf.yml

@@ -32,10 +32,12 @@ jobs:
       with:
         name: PDF
         path: build/latex/LAS.pdf
+        if-no-files-found: error
     - uses: actions/upload-artifact@v4
       with:
         name: Misspelled
         path: build/spelling/output.txt
+        if-no-files-found: ignore