[FIX] P13nConditionPanel: improve date validation
[FIX] P13nConditionPanel: improve date validation

BCP: 1970269196
Change-Id: Ia85d42ba3369f93f4c5ea3d1976ae78b4e30ca71

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5