### Describe the bug

https://github.com/developer-choi/axios-error-report

TypeError is occurred (in 1.6.6 version)

<img width="184" alt="image" src="https://github.com/axios/axios/assets/51902362/1f7f6e7f-8c8b-4ef7-9854-5c08f572d58b">

<img width="171" alt="image" src="https://github.com/axios/axios/assets/51902362/36042439-a071-485e-b696-9f2c01849759">

### To Reproduce

https://github.com/developer-choi/axios-error-report

### Code snippet

_No response_

### Expected behavior

_No response_

### Axios Version

1.6.6

### Adapter Version

_No response_

### Browser

CHROME

### Browser Version

120.0.6099.225

### Node.js Version

20.11.0

### OS

Window 11
test/unit/adapters/http.js
return axios.post('http://localhost:3001/', obj, {
        headers: {
          'content-type': 'application/x-www-form-urlencoded'
        },
        formSerializer: {
          indexes: true
        }
      })
        .then(function (res) {
          assert.strictEqual(res.data, form.toString());
          done();
        }).catch(done);
    });
  });
  describe('Data URL', function () {
    it('should support requesting data URL as a Buffer', function (done) {
      const buffer = Buffer.from('123');
      const dataURI = 'data:application/octet-stream;base64,' + buffer.toString('base64');
      axios.get(dataURI).then(({data})=> {
        assert.deepStrictEqual(data, buffer);
        done();
      }).catch(done);
    });
    it('should support requesting data URL as a Blob (if supported by the environment)', function (done) {
      if (!isBlobSupported) {
        this.skip();
        return;
      }
      const buffer = Buffer.from('123');
      const dataURI = 'data:application/octet-stream;base64,' + buffer.toString('base64');