Filestats check crashing after update to CFE 2.1

Hello,
After an update to CFE 2.1.0p3 (from 2.0.0p8) filestat check on remote host start crashing.Remote host is running Debian 11 and agent updated to 2.1.0p3 but same problem.
There were no issues during upgrade process. Logs bellow.

Thanks in advance.

best regards,
Zeljko

**CMK version:**Checkmk Free Edition 2.1.0p3
**OS version:**Ubuntu 20.04.4 LTS

Error message:

Output of crash.info

{"time": 1656499558.3199532, "os": "Ubuntu 20.04.4 LTS", "version": "2.1.0p3", "edition": "cfe", "core": "cmc", "python_version": "3.9.10 (main, May 11 2022, 12:55:10) \n[GCC 11.2.0]", "python_paths": ["/opt/omd/versions/2.1.0p3.cfe/bin", "/omd/sites/optimamon/local/lib/python3", "/omd/sites/optimamon/lib/python3/plus", "/omd/sites/optimamon/lib/python39.zip", "/omd/sites/optimamon/lib/python3.9", "/omd/sites/optimamon/lib/python3.9/lib-dynload", "/omd/sites/optimamon/lib/python3.9/site-packages", "/omd/sites/optimamon/lib/python3"], "id": "a94876dc-f798-11ec-bb67-8f51a7bb5d1c", "crash_type": "check", "exc_type": "ValueError", "exc_value": "'details' must be non-empty str or None, got ", "exc_traceback": [["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 470, "get_aggregated_result", "result = _aggregate_results("], ["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 578, "_aggregate_results", "perfdata, results = _consume_and_dispatch_result_types(subresults)"], ["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 622, "_consume_and_dispatch_result_types", "for subr in subresults:"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins.py", 94, "filtered_generator", "for element in generator(*args, **kwargs):"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins_legacy.py", 195, "check_result_generator", "yield from _create_new_results_with_details(subresults[idx:])"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins_legacy.py", 227, "_create_new_results_with_details", "yield Result("], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/checking_classes.py", 367, "__new__", "state, summary, details = _create_result_fields(**kwargs)"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/checking_classes.py", 405, "_create_result_fields", "raise ValueError(f\"'{name}' must be non-empty str or None, got {var}\")"]], "local_vars": "eJzogPFN0YXRlLk9LOiAwPiwKICdzdW1tYXJ5JzogJzAgYWRkaXRpb25hbCBkZXRhaWxzIGF2YWlsYWJsZScsCiAndmFyJzogJyd9", "details": {"check_output": "check failed - please submit a crash report!", "host": "Hetzner_proxmox_backup", "is_cluster": false, "description": "File group VM L2BackupFileAgeLDAPSRV01", "check_type": "filestats", "inline_snmp": false, "manual_check": false, "item": "VM L2BackupFileAgeLDAPSRV01", "params": "Parameters({'maxage_newest': (90000, 100800), 'show_all_files': True})", "section": {"VM L2BackupFileAgeLDAPSRV01": ["file_stats", [{"type": "file", "path": "/Backup/ldapsrv01/vzdump-qemu-101-2022_06_27-23_00_03.vma.zst", "stat_status": "ok", "size": 5489612826, "age": 121029, "mtime": 1656378529}, {"type": "file", "path": "/Backup/ldapsrv01/vzdump-qemu-101-2022_06_28-23_00_03.vma.zst", "stat_status": "ok", "size": 5491764091, "age": 34633, "mtime": 1656464925}, {"type": "summary", "count": 2}]], "aix agent files": ["file_stats", [{"type": "summary", "count": 0}]], "$ection with funny characters %s &! (count files in ~)": ["count_only", [{"type": "summary", "count": 3}]]}}}

Agent output

{"time": 1656499558.3199532, "os": "Ubuntu 20.04.4 LTS", "version": "2.1.0p3", "edition": "cfe", "core": "cmc", "python_version": "3.9.10 (main, May 11 2022, 12:55:10) \n[GCC 11.2.0]", "python_paths": ["/opt/omd/versions/2.1.0p3.cfe/bin", "/omd/sites/optimamon/local/lib/python3", "/omd/sites/optimamon/lib/python3/plus", "/omd/sites/optimamon/lib/python39.zip", "/omd/sites/optimamon/lib/python3.9", "/omd/sites/optimamon/lib/python3.9/lib-dynload", "/omd/sites/optimamon/lib/python3.9/site-packages", "/omd/sites/optimamon/lib/python3"], "id": "a94876dc-f798-11ec-bb67-8f51a7bb5d1c", "crash_type": "check", "exc_type": "ValueError", "exc_value": "'details' must be non-empty str or None, got ", "exc_traceback": [["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 470, "get_aggregated_result", "result = _aggregate_results("], ["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 578, "_aggregate_results", "perfdata, results = _consume_and_dispatch_result_types(subresults)"], ["/omd/sites/optimamon/lib/python3/cmk/base/agent_based/checking/__init__.py", 622, "_consume_and_dispatch_result_types", "for subr in subresults:"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins.py", 94, "filtered_generator", "for element in generator(*args, **kwargs):"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins_legacy.py", 195, "check_result_generator", "yield from _create_new_results_with_details(subresults[idx:])"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/register/check_plugins_legacy.py", 227, "_create_new_results_with_details", "yield Result("], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/checking_classes.py", 367, "__new__", "state, summary, details = _create_result_fields(**kwargs)"], ["/omd/sites/optimamon/lib/python3/cmk/base/api/agent_based/checking_classes.py", 405, "_create_result_fields", "raise ValueError(f\"'{name}' must be non-empty str or None, got {var}\")"]], "local_vars": "eydkZXRhaWxzJzogJycsCiAnOiBOb25lLAogJ3N0YXRlJzogPFN0YXRlLk9LOiAwPiwKICdzdW1tYXJ5JzogJzAgYWRkaXRpb25hbCBkZXRhaWxzIGF2YWlsYWJsZScsCiAndmFyJzogJyd9", "details": {"check_output": "check failed - please submit a crash report!", "host": "Hetzner_proxmox_backup", "is_cluster": false, "description": "File group VM L2BackupFileAgeLDAPSRV01", "check_type": "filestats", "inline_snmp": false, "manual_check": false, "item": "VM L2BackupFileAgeLDAPSRV01", "params": "Parameters({'maxage_newest': (90000, 100800), 'show_all_files': True})", "section": {"VM L2BackupFileAgeLDAPSRV01": ["file_stats", [{"type": "file", "path": "/Backup/ldapsrv01/vzdump-qemu-101-2022_06_27-23_00_03.vma.zst", "stat_status": "ok", "size": 5489612826, "age": 121029, "mtime": 1656378529}, {"type": "file", "path": "/Backup/ldapsrv01/vzdump-qemu-101-2022_06_28-23_00_03.vma.zst", "stat_status": "ok", "size": 5491764091, "age": 34633, "mtime": 1656464925}, {"type": "summary", "count": 2}]], "aix agent files": ["file_stats", [{"type": "summary", "count": 0}]], "$ection with funny characters %s &! (count files in ~)": ["count_only", [{"type": "summary", "count": 3}]]}}}