CI: Github actions fix commit status on new PR

On windows tester actions we are adding the status to the latest commit on a PR; to get the commit
value we inspect the gh context but the condition to get the value on a new PR (.event.after is null) is not catch by the expression and so the .sha value is not picked; as so the status is not correctly added to the commit. This fix extends the condition to check for null values; and if that is the case pick the right commit value

Signed-off-by: Adrian Riobo Lorenzo <ariobolo@redhat.com>

.github/workflows/windows-qe-tpl.yml

@@ -56,9 +56,9 @@ jobs:
       run: |
         # Get origin commit sha for testing
         commit_sha=$(cat gh_context.json | jq -r '.event.after')
-        if [[ -z "${commit_sha}" ]]; then
+        if [[ -z "${commit_sha}" ]] || [[ "${commit_sha}" == null ]]; then
           # on first PR creation .event.after is empty, then .sha is used as commit instead
-          commit_sha=$(cat gh_context.json | jq -r '.sha')
+          commit_sha=$(cat gh_context.json | jq -r '.event.pull_request.head.sha')
         fi
         echo "commit_sha=${commit_sha}" >> "$GITHUB_ENV"