fix(ls): let --domains answer nothing instead of raising

alakazam.py

@@ -60,7 +60,7 @@ SETTINGS_PATH = ""  # path to the alakazam settings file
 GROUP_PATH = None  # path this run was invoked with, either an instance file or a group directory
 HIDE_SECRETS = False  # keep secret values out of the output, for runs whose logs are archived
 ABRA_DIR = None  # path to the abra data directory
-FETCH_MAX_AGE = 600 # seconds; recipe repos are refetched at most once per hour
+FETCH_MAX_AGE = 3600 # seconds; recipe repos are refetched at most once per hour
 ABRA_RETRIES = 6 # number of attempts per abra command that failed to reach the server
 ABRA_RETRY_DELAY = 2 # seconds before the first retry, doubled for every further one
 # lower case markers in the abra output that indicate an unreachable server instead of a failed operation
@@ -2141,7 +2141,8 @@ def ls(recipes: Tuple[str], deployed: bool, undeployed: bool, domains: bool, ser
     else:
         instance_apps = get_apps(recipes)
     if domains:
-        print(list(zip(*sum(instance_apps.values(), [])))[1])
+        if apps_domains := sum(instance_apps.values(), []):
+            print(list(zip(*apps_domains))[1])
     else:
         print_all_apps(instance_apps)