diseaseObservation property Null safety

1. farmershands
2. disease_observation_create_screen_vm
3. DiseaseObservationCreateScreenVM
4. diseaseObservation property

DiseaseObservationCreateScreenVM class

1. Constructors
2. DiseaseObservationCreateScreenVM
3. Properties
4. appearance
5. appearanceRadios
6. bcs
7. bcsRadios
8. buttonTitle
9. context
10. currentGroup
11. dehydration
12. dehydrationRadios
13. diseaseObservation
14. ear
15. earRadios
16. eye
17. eyeRadios
18. feces
19. fecesRadios
20. hashCode
21. hasListeners
22. inputMode
23. memo
24. memoController
25. respiAndCough
26. respiAndCoughRadios
27. runtimeType
28. sensorPosition
29. sensorPositionRadios
30. snot
31. snotRadios
32. temperatureController
33. Methods
34. addListener
35. changeRadioSelect
36. dispose
37. init
38. noSuchMethod
39. notifyListeners
40. onSubmitCreateDiseaseObservation
41. removeListener
42. setAppearance
43. setBCS
44. setCow
45. setCreateMode
46. setCurrentGroup
47. setDehydration
48. setEar
49. setEye
50. setFeces
51. setInputMode
52. setMemo
53. setRespAndCough
54. setSensorPosition
55. setSnot
56. setUpdateMode
57. toString
58. Operators
59. operator ==