Do not run upload actions if env var is not set

ABLY_AWS_ACCOUNT_ID_SDK is an org level secret that will not be available to anybody outside of the Ably org, like dependabot. To prevent failures from PRs opened by dependabot et al, do run the upload steps.

.github/workflows/dev-ci.yml

@@ -72,12 +72,20 @@ jobs:
         run: npm run docs
       - name: Configure AWS Credentials
         uses: aws-actions/configure-aws-credentials@v1
+        env:
+          ably_aws_account_id_sdk: ${{ secrets.ABLY_AWS_ACCOUNT_ID_SDK }}
+        # do not run if these variables are not available; they will not be available for anybody outside the Ably org
+        if: ${{ env.ably_aws_account_id_sdk != '' }} 
         with:
           aws-region: eu-west-2
           role-to-assume: arn:aws:iam::${{ secrets.ABLY_AWS_ACCOUNT_ID_SDK }}:role/ably-sdk-builds-spaces
           role-session-name: "${{ github.run_id }}-${{ github.run_number }}"
       - name: Upload Documentation
         uses: ably/sdk-upload-action@v1
+        env:
+          ably_aws_account_id_sdk: ${{ secrets.ABLY_AWS_ACCOUNT_ID_SDK }}
+        # do not run if these variables are not available; they will not be available for anybody outside the Ably org
+        if: ${{ env.ably_aws_account_id_sdk != '' }}
         with:
           sourcePath: docs/typedoc/generated
           githubToken: ${{ secrets.GITHUB_TOKEN }}