Element muxed not found (flutter youtube_extractor)

[younisHazim]

hello
I have a problem
I can't get a video muxed with sound but can get video or sound only without muxed

there are error

E/flutter ( 9171): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: Bad state: No element E/flutter ( 9171): #0 List.first (dart:core-patch/growable_array.dart:219:5) E/flutter ( 9171): #1 _HomePageState._getDownloadLink (package:download_from_youtube/main.dart:154:46) E/flutter ( 9171): <asynchronous suspension> E/flutter ( 9171): #2 _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:772:19) E/flutter ( 9171): #3 _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:855:36) E/flutter ( 9171): #4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24) E/flutter ( 9171): #5 TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:504:11) E/flutter ( 9171): #6 BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:282:5) E/flutter ( 9171): #7 BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:217:7) E/flutter ( 9171): #8 PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:475:9) E/flutter ( 9171): #9 PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:76:12) E/flutter ( 9171): #10 PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:122:9) E/flutter ( 9171): #11 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8) E/flutter ( 9171): #12 PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:120:18) E/flutter ( 9171): #13 PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:106:7) E/flutter ( 9171): #14 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:218:19) E/flutter ( 9171): #15 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22) E/flutter ( 9171): #16 GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7) E/flutter ( 9171): #17 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7) E/flutter ( 9171): #18 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7) E/flutter ( 9171): #19 _rootRunUnary (dart:async/zone.dart:1196:13) E/flutter ( 9171): #20 _CustomZone.runUnary (dart:async/zone.dart:1085:19) E/flutter ( 9171): #21 _CustomZone.runUnaryGuarded (dart:async/zone.dart:987:7) E/flutter ( 9171): #22 _invoke1 (dart:ui/hooks.dart:275:10) E/flutter ( 9171): #23 _dispatchPointerDataPacket (dart:ui/hooks.dart:184:5) E/flutter ( 9171):