panic: NewTypeDecl: fail to complete type mi_block_s: error convert type: unsupported type <nil>

Its source code:

typedef struct mi_block_s {
  _Atomic(mi_encoded_t) next;
} mi_block_t;

AST:
mi_encoded_t:

 "Name": {
          "Name": "mi_encoded_t",
          "_Type": "Ident"
        },
        "Parent": null,
        "Type": {
          "Name": "uintptr_t",
          "_Type": "Ident"
        },
        "_Type": "TypedefDecl"

_Atomic(mi_encoded_t):

createBaseField: ProcessType _Atomic(mi_encoded_t) TypeKind: Atomic      
ProcessType: TypeName: _Atomic(mi_encoded_t) TypeKind: Atomic
ProcessType: Unknown Type TypeName: _Atomic(mi_encoded_t) TypeKind: Atomic

     {
        "Doc": {
          "List": [
            {
              "Text": "// free lists contain blocks\n",
              "_Type": "Comment"
            }
          ],
          "_Type": "CommentGroup"
        },
        "Loc": {
          "File": "/opt/homebrew/opt/python@3.13/Frameworks/Python.framework/Versions/3.13/include/python3.13/internal/mimalloc/mimalloc/types.h",
          "_Type": "Location"
        },
        "Name": {
          "Name": "mi_block_s",
          "_Type": "Ident"
        },
        "Parent": null,
        "Type": {
          "Fields": {
            "List": [
              {
                "Access": 1,
                "Comment": null,
                "Doc": null,
                "IsStatic": false,
                "Names": [
                  {
                    "Name": "next",
                    "_Type": "Ident"
                  }
                ],
                "Type": null,
                "_Type": "Field"
              }
            ],
            "_Type": "FieldList"
          },
          "Methods": null,
          "Tag": 0,
          "_Type": "RecordType"
        },
        "_Type": "TypeDecl"
      },

Reproduce the panic with the shown mi_block_s declaration and the _Atomic(mi_encoded_t) field, using the AST and type-processing output in the issue as reference. Trace the Atomic type handling and conversion path; done means this declaration no longer panics and the field type is processed successfully.