PollOptionHandler constructor Null safety

1. sendbird_sdk
2. poll_option_handler
3. PollOptionHandler
4. PollOptionHandler constructor

PollOptionHandler class

1. Constructors
2. PollOptionHandler
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. onResult
9. toString
10. Operators
11. operator ==