Fix syntax for BENCH_TAG in workflow file

Author: Malmahrouqi3

.github/workflows/bench-frontier.yml

@@ -44,7 +44,7 @@ jobs:
     env:
       ACTIONS_RUNNER_FORCE_ACTIONS_NODE_VERSION: node16
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
-      BENCH_TAG: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.tag != '' ? github.event.inputs.tag: 'v5.1.3' }}
+      BENCH_TAG: "${{ github.event_name == 'workflow_dispatch' && github.event.inputs.tag != '' ? github.event.inputs.tag : 'v5.1.3' }}"
     steps:
       - name: Clone - PR
         uses: actions/checkout@v4