Bad state: No element

[frankmer]

[ERROR] Stacktrace:
[ERROR] 0 Iterable.lastWhere (dart:core/iterable.dart:733)
[ERROR] 1 NavigatorState.pop (package:flutter/src/widgets/navigator.dart:5243)
[ERROR] 2 Navigator.pop (package:flutter/src/widgets/navigator.dart:2569)
[ERROR] 3 QRScannerView.build. (package:privacyidea_authenticator/views/qr_scanner_view/qr_scanner_view.dart:48)
[ERROR] 4 _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1183)
[ERROR] 5 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:275)
[ERROR] 6 TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:652)
[ERROR] 7 BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:309)
[ERROR] 8 BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:279)
[ERROR] 9 GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:167)
[ERROR] 10 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:492)
[ERROR] 11 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:468)
[ERROR] 12 RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:439)
[ERROR] 13 GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:413)
[ERROR] 14 GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:376)
[ERROR] 15 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:323)
[ERROR] 16 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:292)
[ERROR] 17 _rootRunUnary (dart:async/zone.dart:1415)
[ERROR] 18 _CustomZone.runUnary (dart:async/zone.dart:1308)
[ERROR] 19 _CustomZone.runUnaryGuarded (dart:async/zone.dart:1217)
[ERROR] 20 _invoke1 (dart:ui/hooks.dart:330)
[ERROR] 21 PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:410)
[ERROR] 22 _dispatchPointerDataPacket (dart:ui/hooks.dart:262)