ExternalLoginAuthenticationManager.java should catch a expeption

[lijjhaha]

line 112,

if idTokenWasIssuedByTheUaa, then isAddNewShadowUser will throw a ClassCastException excption caught by servlet.
it's better to catch this exception and throw a AccountNotPreCreatedException.
as below:

    if (userFromDb == null) {
        try{
             if (!isAddNewShadowUser(origin)) {
                 throw new AccountNotPreCreatedException("The user account must be pre-created. Please contact your system administrator.");
             }
        }catch(ClassCastException e){  
            throw new AccountNotPreCreatedException("The user account must be pre-created. Please contact your system administrator.");
         }


        publish(new NewUserAuthenticatedEvent(userFromRequest.authorities(List.of())));
        try {
            userFromDb = userDatabase.retrieveUserByName(userFromRequest.getUsername(), origin);
        } catch (UsernameNotFoundException ex) {
            throw new BadCredentialsException("Unable to register user in internal UAA store.");
        }
    }