Crash on saving maps 4.5

Hi, this is urgent could someone tell me how i could fix this problem, what im doing is right clicking on the current map in the content browser so i can duplicate it twice, I didnt rename the other two just yet but they still have a different name and when i try to save all levels so i can work on the other maps it crashes everytime.

MachineId:
UserName

Thats all i can get from the crash reported

Hey Izzy,

This feature has actually been taken out of the editor for the time being in the newer version of UE4. However, since you’re still working out of 4.5, if you create a blank map and load it, you should be able to then duplicate the map you were trying to originally duplicate. I was able to get around the crash by doing it that way in the older version of the editor. Just make sure the map you’re not trying to duplicate is the one loaded before duplicating.

Cheers!