[2.3.0] Checkmk Werk 16623 created: HW/SW Inventory: Fix crash when filtering for number of sites for Checkmk version

[//]: # (werk v2) # HW/SW Inventory: Fix crash when filtering for number of sites for Checkmk version key | value ---------- | --- compatible | yes version | 2.3.0b3 date | 2024-03-11T14:37:28+00:00 level | 1 class | fix component | inv edition | cre When filtering the Checkmk versions -> #Sites inventory column, a crash occurs with ``` TypeError (expected string or bytes-like object) ... File "/omd/sites/oldstable/lib/python3/cmk/gui/query_filters.py", line 510, in <lambda> return lambda row: bool(regex.search(row.get(column, ""))) ``` This crash has been fixed.