Put simply, none of your data is viewable by me. If the app requests your location, it's just with Apple's APIs and for the functioning of the app. None of this data leaves your device. Any data that is synced through Apple's iCloud service is also not viewable by me.
Although the app does not collect any data, TrailsTracker makes use of a third party service for displaying the maps:
I use Apple's built in service for crash data. I can only view your type of device, version of iOS and the date when the crash occurred. Also the steps which were taken before the app crashed. However no personal identifiable information is viewable by me.