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Open settings then Apps and swipe to all and find on the list the app that has become default then open it and choose clear cache then see if your app option is back
Try Thommo's suggestion,if not working,just settings-apps-all-media storage,clear defaults.
What photo editor did you choose by default?google photos?
Do this:open the app,tap longer on home to get the recent task manager,tap longer on your app,select app info,go to settings and clear defaults.
If you have the option to reset app preferences, click that. All it does it reset all the default options you have setted for any apps, doesn't delete anything.