fix: Only include actorStandby when at least one field is provided

Update the `get_actor_representation` function to conditionally include
the `actorStandby` object only when at least one of its fields is not None.
This prevents sending empty or null-only actorStandby objects to the API.

According to the API changes, actorStandby is optional and should only be
included when needed, with isEnabled being the only required field within
the object when present.

Related JS client issue: apify/apify-client-js#832

Closes #595

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: vdusek

src/apify_client/clients/resource_clients/actor.py

@@ -62,7 +62,7 @@ def get_actor_representation(
     actor_permission_level: ActorPermissionLevel | None = None,
 ) -> dict:
     """Get dictionary representation of the Actor."""
-    return {
+    actor_dict = {
         'name': name,
         'title': title,
         'description': description,
@@ -85,17 +85,31 @@ def get_actor_representation(
             'body': example_run_input_body,
             'contentType': example_run_input_content_type,
         },
-        'actorStandby': {
+        'pricingInfos': pricing_infos,
+        'actorPermissionLevel': actor_permission_level,
+    }
+
+    # Only include actorStandby if at least one field is provided
+    if any(
+        [
+            actor_standby_is_enabled is not None,
+            actor_standby_desired_requests_per_actor_run is not None,
+            actor_standby_max_requests_per_actor_run is not None,
+            actor_standby_idle_timeout_secs is not None,
+            actor_standby_build is not None,
+            actor_standby_memory_mbytes is not None,
+        ]
+    ):
+        actor_dict['actorStandby'] = {
             'isEnabled': actor_standby_is_enabled,
             'desiredRequestsPerActorRun': actor_standby_desired_requests_per_actor_run,
             'maxRequestsPerActorRun': actor_standby_max_requests_per_actor_run,
             'idleTimeoutSecs': actor_standby_idle_timeout_secs,
             'build': actor_standby_build,
             'memoryMbytes': actor_standby_memory_mbytes,
-        },
-        'pricingInfos': pricing_infos,
-        'actorPermissionLevel': actor_permission_level,
-    }
+        }
+
+    return actor_dict
 
 
 class ActorClient(ResourceClient):