CI: Linux: Dont fail if dockerhub_username is not set

Signed-off-by: Luis Garcia <git@luigi311.com>

.github/workflows/release-linux.yml

@@ -95,7 +95,7 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: |
-            ikatson/rqbit
+            ${{ vars.DOCKERHUB_USERNAME }}/rqbit, enable=${{ vars.DOCKERHUB_USERNAME != '' }}
           tags: |
             type=ref,event=branch
             type=semver,pattern={{version}}
@@ -120,6 +120,8 @@ jobs:
         uses: docker/setup-buildx-action@v3
 
       - name: Login to Docker Hub
+        if: "${{ vars.DOCKERHUB_USERNAME != '' }}"
+        id: docker_login
         uses: docker/login-action@v3
         with:
           username: ${{ vars.DOCKERHUB_USERNAME }}
@@ -128,7 +130,7 @@ jobs:
       - name: Build and push
         uses: docker/build-push-action@v6
         with:
-          push: true
+          push: ${{ steps.docker_login.outcome == 'success' }}
           tags: ${{ steps.meta.outputs.tags }}
           platforms: linux/amd64,linux/arm64,linux/arm/v7
           context: target/cross/