bundles/wireguard: fix KeyError when running with no peers

bundles/wireguard/metadata.py

@@ -262,17 +262,19 @@ def health_checks(metadata):
 
         checks[peer] = config['their_ip']
 
-    if not checks:
-        return {}
-
-    return {
-        'systemd-timers': {
-            'timers': {
+    if checks:
+        timer = {
             'wg-health-check': {
                 'command': '/usr/local/bin/wg_health_check',
                 'when': 'minutely',
             },
-            },
+        }
+    else:
+        timer = {}
+
+    return {
+        'systemd-timers': {
+            'timers': timer,
         },
         'wireguard': {
             'health_checks': checks,