Fix CLM configuration error (#29)

The "filter" field is optional, ensure it is present before setting the
environment variable.

Refs  NethServer/dev#7061

imageroot/actions/set-clm-forwarder/10set

@@ -22,7 +22,8 @@ if not bool(subscription):
 if (request['active']):
     agent.set_env('CLOUD_LOG_MANAGER_ADDRESS', f"{request['address']}")
     agent.set_env('CLOUD_LOG_MANAGER_TENANT', f"{request['tenant']}")
-    agent.set_env('CLOUD_LOG_MANAGER_FILTER', f"{request['filter']}")
+    if 'filter' in request:
+        agent.set_env('CLOUD_LOG_MANAGER_FILTER', request['filter'])
 
     if 'start_time' in request and request['start_time'] != '':
         agent.set_env('CLOUD_LOG_MANAGER_START_TIME', f"{request['start_time']}")