ci(release.yaml): make 'merge into develop' task optional

.github/workflows/release.yaml

@@ -116,9 +116,13 @@ jobs:
 
       - name: 📤 merge into develop
         run: |
+          if git show-ref --quiet refs/heads/develop; then
             git checkout develop
             git merge main
             git push origin develop
+          else
+            echo "develop doesn't exist, skipping..."
+          fi
 
       - name: ✅ done
         run: echo "done"