getCueById method Null safety

1. Flutter
2. dart:html
3. TextTrackCueList
4. getCueById method

TextTrackCueList class

1. Properties
2. first
3. hashCode
4. isEmpty
5. isNotEmpty
6. iterator
7. last
8. length
9. reversed
10. runtimeType
11. single
12. Methods
13. add
14. addAll
15. any
16. asMap
17. cast
18. clear
19. contains
20. elementAt
21. every
22. expand
23. fillRange
24. firstWhere
25. fold
26. followedBy
27. forEach
28. getCueById
29. getRange
30. indexOf
31. indexWhere
32. insert
33. insertAll
34. join
35. lastIndexOf
36. lastIndexWhere
37. lastWhere
38. map
39. noSuchMethod
40. reduce
41. remove
42. removeAt
43. removeLast
44. removeRange
45. removeWhere
46. replaceRange
47. retainWhere
48. setAll
49. setRange
50. shuffle
51. singleWhere
52. skip
53. skipWhile
54. sort
55. sublist
56. take
57. takeWhile
58. toList
59. toSet
60. toString
61. where
62. whereType
63. Operators
64. operator +
65. operator ==
66. operator []
67. operator []=