Added ternary operator for ref to docker deploy

Signed-off-by: Andre Wanlin <awanlin@spotify.com>

.github/workflows/deploy_docker-image.yml

@@ -5,6 +5,9 @@ on:
   repository_dispatch:
     types: [release-published]
 
+env:
+  RELEASE_VERSION: v${{ github.event.client_payload.version }}
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -24,7 +27,7 @@ jobs:
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           path: backstage
-          ref: v${{ github.event.client_payload.version }}
+          ref: ${{ github.event.client_payload.version && env.RELEASE_VERSION || github.ref }}
 
       - name: use node.js ${{ matrix.node-version }}
         uses: actions/setup-node@60edb5dd545a775178f52524783378180af0d1f8 # v4.0.2