updating failed the child recode while saving the parent

Question

hi ,

i  Have two table "Customer"  & "VisitorSession" 

Visitorsettion have the foreign key constraint with customer  please see the bellow image


when i try to insert new customer i am getting the following error that "An error occurred while updating the entries. See the inner exception for details."
in my research I found the visitor session last recode is update with the fkCustomerId value is 0 that is zero is coming from the newcustomer object so we get the error but int he code i didn't pass any values to this visitorsession navigation values while debug if found the navigation collection count is "0" any one please guid me how can i come out this problem . debug image is as follows