I was just testing my app on the ios12 Beta, and when the app tried switching to the camera, it crashed.
It seems that you need to include a Privacy - Microphone Usage Description. After adding that, switching to the camera prompted for microphone access.
Please file a radar about these issues. Obviosuly we should not be crashing, and the dialog should probably be corrected.
I suspect you're getting the Microphone Usage requirement because the camera is capable of taking live photos, which also capture a couple of seconds of sound.
I ran into the same problem, and filed radar #40897667 with a sample project that demonstrates the problem.
This is noted in the release notes:
UIKit New Issues • Presenting a UIImagePickerController might cause the app to be terminated with a privacy violation if the app does not include the NSMicrophoneUsageDescription key in its Info.plist. (40490417) Workaround: Add the NSMicrophoneUsageDescription key to the application’s Info.plist.
