unmarshal does not return nil object when value is nil

[Iceber]

issue: containerd/containerd#8392

For unmarshal, thevalue param is nil, it does not mean that typeurl is also empty.
When value is nil, the unmarshal returns nil, nil directly, which becomes cumbersome to use and skips the check for typeurl.

Always have unmarshal return a non-nil object when err is nil, which is consistent with the behavior of v1 typeurl

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (2a94991) 68.90% compared to head (7f96cad) 68.90%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #41   +/-   ##
=======================================
  Coverage   68.90%   68.90%           
=======================================
  Files           1        1           
  Lines         119      119           
=======================================
  Hits           82       82           
  Misses         28       28           
  Partials        9        9           

Impacted Files	Coverage Δ
types.go	68.90% <100.00%> (ø)

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[fuweid]

IIUC, it should be if len(value) == 0.

[Iceber]

After some thought, I decided to remove this judgment and bring the behavior in here back to be consistent with v1typeurl.

For proto, the empty value(nil, []byte{}) needs to set all the fields of the incoming v parameter to empty, because maybe the incoming v object already has some fields set

For json, it should not be nil or []byte{}, a valid null value is "null" or '{}', '[]', if value is nil or []byte{}, then json.Marshal will return an error

[fuweid]

LGTM

[Iceber]

@fuweid @kzys Are we ready to release v2.1.1? I want to update to containerd and release/1.7

[fuweid]

I will push a tag next Monday if no one takes this. @Iceber

[Iceber]

@fuweid Could we release 2.1.1 now? 😀

[fuweid]

@Iceber Done.