loxigen-artifacts: address review comments
diff --git a/.abat-automerge b/.abat-automerge
index 90679df..772134b 100755
--- a/.abat-automerge
+++ b/.abat-automerge
@@ -5,6 +5,6 @@
 ln -sf ../../.hooks/pre-commit .git/hooks/pre-commit
 make all check-all
 
-if [[ $ARTIFACT_REPO_URL ]]; then
+if [[ ${ARTIFACT_REPO_URL-} ]]; then
     ./.build/push-artifacts.sh ${ARTIFACT_REPO_URL}
 fi