AbpAccountWebModule, checkPassword method throw exception when username is not registed

[crashsol]

  [HttpPost]
    [Route("checkPassword")]
    public virtual async Task<AbpLoginResult> CheckPassword(UserLoginInfo login)
    {
        ValidateLoginInfo(login);
        var identityUser = await _userManager.FindByNameAsync(login.UserNameOrEmailAddress);
        return GetAbpLoginResult(await _signInManager.CheckPasswordSignInAsync(identityUser, login.Password, true));
    }
  identityUser maybe null,  need repaired