fix(worker): accept omitted empty image command

tests/test_worker_006_agent_image_installer.py

@@ -37,6 +37,9 @@ def test_worker_agent_installer_is_local_offline_and_non_buildkit() -> None:
         "\\\"k1link.observatory.m49_worker_container_main\\\"]'"
     ) in script
     assert 'title="NODE.DC Observatory Worker 006 agent"' not in script
+    assert '$Image.Config.PSObject.Properties["Cmd"]' in script
+    assert "$null -ne $commandProperty" in script
+    assert "@($commandProperty.Value).Count -ne 0" in script
     assert "docker rm -f $containerId" in script
     assert "docker rm -f $containerName" not in script