Tools: Fixed Docker login for CI

.github/workflows/github-actions-main.yml

@@ -41,8 +41,11 @@ jobs:
         with:
           node-version: '12'
 
+      # Login to Docker only if we're on a server release tag. If we run this on
+      # a pull request it will fail because the PR doesn't have access to
+      # secrets
       - uses: docker/login-action@v1
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && startsWith(github.ref, 'refs/tags/server-v')
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}