Obrigado @rmaddy, eu adicionei isso logo após outros pares de chaves no Info.plist e corrigi o problema:
<key>NSPhotoLibraryUsageDescription</key>
<string>Photo Library Access Warning</string>
Editar:
Também acabei tendo problemas semelhantes em diferentes componentes do meu aplicativo. Acabamos adicionando todas essas chaves até agora (após a atualização para o Xcode8 / iOS10):
<key>NSPhotoLibraryUsageDescription</key>
<string>This app requires access to the photo library.</string>
<key>NSMicrophoneUsageDescription</key>
<string>This app does not require access to the microphone.</string>
<key>NSCameraUsageDescription</key>
<string>This app requires access to the camera.</string>
Confira este link developer.apple.com para obter a lista completa de referências de chave da lista de propriedades.
Lista completa:
Música da Apple:
<key>NSAppleMusicUsageDescription</key>
<string>My description about why I need this capability</string>
Bluetooth:
<key>NSBluetoothPeripheralUsageDescription</key>
<string>My description about why I need this capability</string>
Calendário:
<key>NSCalendarsUsageDescription</key>
<string>My description about why I need this capability</string>
Câmera:
<key>NSCameraUsageDescription</key>
<string>My description about why I need this capability</string>
Contatos:
<key>NSContactsUsageDescription</key>
<string>My description about why I need this capability</string>
FaceID:
<key>NSFaceIDUsageDescription</key>
<string>My description about why I need this capability</string>
Partilha de Saúde:
<key>NSHealthShareUsageDescription</key>
<string>My description about why I need this capability</string>
Atualização de saúde:
<key>NSHealthUpdateUsageDescription</key>
<string>My description about why I need this capability</string>
Kit em casa:
<key>NSHomeKitUsageDescription</key>
<string>My description about why I need this capability</string>
Localização:
<key>NSLocationUsageDescription</key>
<string>My description about why I need this capability</string>
Localização (sempre):
<key>NSLocationAlwaysUsageDescription</key>
<string>My description about why I need this capability</string>
Localização (Quando em uso):
<key>NSLocationWhenInUseUsageDescription</key>
<string>My description about why I need this capability</string>
Microfone:
<key>NSMicrophoneUsageDescription</key>
<string>My description about why I need this capability</string>
Movimento (acelerômetro):
<key>NSMotionUsageDescription</key>
<string>My description about why I need this capability</string>
NFC (comunicação em campo próximo):
<key>NFCReaderUsageDescription</key>
<string>My description about why I need this capability</string>
Biblioteca de fotos:
<key>NSPhotoLibraryUsageDescription</key>
<string>My description about why I need this capability</string>
Biblioteca de fotos (acesso somente gravação):
<key>NSPhotoLibraryAddUsageDescription</key>
<string>My description about why I need this capability</string>
Lembretes:
<key>NSRemindersUsageDescription</key>
<string>My description about why I need this capability</string>
Siri:
<key>NSSiriUsageDescription</key>
<string>My description about why I need this capability</string>
Reconhecimento de fala:
<key>NSSpeechRecognitionUsageDescription</key>
<string>My description about why I need this capability</string>
NSPhotoLibraryUsageDescription
e você encontrará muitos exemplos.