Hello there! Please follow the steps below to fix iphoto.
open a finder window or folder window
hold shift then click on go from the tool bar
then select library
go to Preferences
here look for com.apple.iphoto or com.apple.iapps.
then move the file to your desktop
restart your mac by clicking the apple icon and select reset/ restart.
then try and open iphoto after your mac resets :)