Update antora-generator.yml

Only trigger generator if the PR has access to the required secrets.

Author: philipwindecker

.github/workflows/antora-generator.yml

@@ -12,13 +12,17 @@ jobs:
     name: Trigger antora generator
 
     runs-on: Ubuntu-latest
-
+    
+    env:
+      MUP_KEY: ${{ secrets.MACHINE_USER_PAT }}
+    
     steps:
     - name: Trigger generator
+      if: ${{ env.MUP_KEY != '' }}
       uses: peter-evans/repository-dispatch@v2
       with:
         token: ${{ secrets.MACHINE_USER_PAT }}
         event-type: antora-build-trigger
         repository: OpenSimulationInterface/osi-antora-generator
         client-payload: '{"src": "${{ github.repository }}", "ref": "${{ github.ref }}", "sha": "${{ github.sha }}", "head_ref": "${{ github.head_ref }}"}'
-        
+