ci: fix the error of release condition

Author: HelloWRC

.github/workflows/build.yml

@@ -28,7 +28,7 @@ jobs:
         dotnet nuget add source --username HelloWRC --password $env:GHPKG_KEY --store-password-in-clear-text --name github "https://nuget.pkg.github.com/ClassIsland/index.json"
         dotnet nuget push .\out\*.nupkg -k $env:GHPKG_KEY --source "github" --skip-duplicate
     - name: Upload Nuget packages to NuGet Gallery
-      if: ${{ github.event.inputs.release_tag && github.event_name != 'pull_request' }}
+      if: ${{ startsWith(github.ref, 'refs/tags/') && github.event_name != 'pull_request' }}
       env:
         NUGET_KEY: ${{ secrets.NUGET_ORG_KEY }}
       run: |