i cant delete or create any worlds i can make a world it wont be saved

Put the summary of the bug you're having here

What i expected to happen was...:
that if i go back to the title screen and press play game my world would be in the list
and i tried to delete a world and i tought it would delete
What actually happened was...:
i could not find my newly created world and al worlds where set to creative
and as i clicked delete the old world just wouldnt disapear

Steps to Reproduce:
1.click create world
2.go back to title screen
3. and its gone