OpenHAB rule not working after persistence reset

[dersimn]

Due to current implementation of this line in wifi_detection.rules, persistence detection is not working under the following circumstances:

• When Persistence of the items Person_X_Wifi_LastSeen_Seconds is not set to restore on startup and one or more people are not at home when OpenHAB is started
• Persistence cache got wiped while one or more people were not at home.

Log will show the error: Error during the execution of rule Wifi Detection: java.lang.Number. This is because line throws an error if Person_X_Wifi_LastSeen_Seconds is undefined (for e.g. after a restart or wipe of persistence cache) the remaining rule functions are not executed and the wifi detection can't work properly.