nullable TransferRequest1_1.RestartChannel

[turuslan]

Fixes ambiguos TransferRequest1_1.RestartChannel cbor encoding - make it nullable.

[codecov-commenter]

Codecov Report

Merging #315 (4a1455d) into master (48303da) will decrease coverage by 0.12%.
The diff coverage is 41.17%.

@@            Coverage Diff             @@
##           master     #315      +/-   ##
==========================================
- Coverage   66.06%   65.94%   -0.13%     
==========================================
  Files          29       29              
  Lines        3439     3450      +11     
==========================================
+ Hits         2272     2275       +3     
- Misses        814      818       +4     
- Partials      353      357       +4     

Impacted Files	Coverage Δ
message/message1_1/transfer_request.go	57.74% <33.33%> (-1.68%)	⬇️
message/message1_1/transfer_request_cbor_gen.go	28.78% <33.33%> (+0.49%)	⬆️
message/message1_1prime/transfer_request.go	66.66% <33.33%> (-2.30%)	⬇️
message/message1_1/message.go	55.93% <100.00%> (ø)
message/message1_1prime/message.go	53.90% <100.00%> (ø)