Merge pull request #2342 from freifunk-gluon/ci-fixes

.github/workflows/build-gluon.yml

-
-# Update this file after adding/removing/renaming a target by running
-# `make list-targets BROKEN=1 | ./contrib/actions/generate-actions.py > ./.github/workflows/build-gluon.yml`
-
 name: Build Gluon
 on:
   push:
@@ -28,6 +24,7 @@ jobs:
 
   build_firmware:
     needs: changed
+    if: ${{ needs.changed.outputs.targets != '[]' && needs.changed.outputs.targets != '' }}
     strategy:
       fail-fast: false
       matrix: