Add null-glob guard for .deb files before dpkg install

Agent-Logs-Url: https://github.com/nextcloud/documentation/sessions/872269b8-1ded-4db5-8d42-72115ccab6fa

Co-authored-by: skjnldsv <14975046+skjnldsv@users.noreply.github.com>

Author: Copilot

.github/workflows/sphinxbuild.yml

@@ -140,7 +140,12 @@ jobs:
         if: ${{ matrix.manual.build_pdf_path }}
         timeout-minutes: 5
         run: |
-          sudo dpkg -i --force-depends ${{ runner.temp }}/.cache/archives/*.deb
+          debs=(${{ runner.temp }}/.cache/archives/*.deb)
+          if [ ! -e "${debs[0]}" ]; then
+            echo "No .deb files found in cache archives — cache may be empty or missing." >&2
+            exit 1
+          fi
+          sudo dpkg -i --force-depends "${debs[@]}"
           sudo DEBIAN_FRONTEND=noninteractive apt-get install -f -y --no-install-recommends \
             -o Dir::State::lists="${{ runner.temp }}/.cache/lists"