fix cicd error when branch creation

Author: zhogu

.github/workflows/build-deploy-changes.yaml

@@ -49,7 +49,12 @@ jobs:
             base_sha=$(git merge-base origin/${{ github.event.pull_request.base.ref }} ${{ github.event.pull_request.head.sha }})
             head_sha="${{ github.event.pull_request.head.sha }}"
           else
-            base_sha="${{ github.event.before }}"
+            if [ "${{ github.event.before }}" = "0000000000000000000000000000000000000000" ]; then
+              # Get the previous commit on branch
+              base_sha=$(git rev-parse ${{ github.sha }}^)
+            else
+              base_sha="${{ github.event.before }}"
+            fi
             head_sha="${{ github.sha }}"
           fi