Fix yml syntax for action

Author: mike-potter

.github/workflows/default.yml

@@ -55,7 +55,7 @@ jobs:
         uses: docker/setup-buildx-action@v1
 
       - name: Login to DockerHub
-        if: github.event_name != 'pull_request' && secrets.DOCKERHUB_ORG != ''
+        if: ${{ github.event_name }} != 'pull_request' && ${{ secrets.DOCKERHUB_ORG }} != ''
         uses: docker/login-action@v1
         with:
           username: ${{ secrets.DOCKERHUB_USER }}