removeItem method Null safety

1. Dart
2. dart:svg
3. NumberList
4. removeItem method

NumberList class

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