Fix error on configuration date field

Summary

wenn ich Tree by Configuration at date wähle und die Zeit händisch eingebe - kommt die Fehlermeldung "Loading of Configuration tree failed"

Steps to reproduce

• go to configurations/123/platforms-and-devices
• edit the date picker field manually
• a warning message will show up when an incorrect date format is picked

What is the expected correct behavior?

no warning should show until a valid date is entered

Possible fixes

add validation to watcher function

ToDo's

• Bug reproduced
• Cause found
• Bug fixed