Hi rranon,
According to this link:
seems like if you are compiling your app against the new iOS SDK 10, you need to add an extra key/value pair to your info.plist file to have camera access.
(If you are using the previous iOS 9 SDK, like I do the app will work on both iOS9 and iOS 10 without the extra key/value pair)
Add permission in info.plist file base on your error log.
NSCameraUsageDescription
<key>NSCameraUsageDescription</key>
<string>$(PRODUCT_NAME) camera use.</string>
In UE4 ->Project settings -> iOS there is an extra PList data field, where you can add the text above.