Gemini API call, sending image over network

I initially used local upload for image, but was having difficulty in converting the file directly because it was of type FFUploadByte or something like that. Then I uploaded images directly to firebase such that I could simply fetch the URL and send it over network. But I was getting this response:
{

"error": {

"code": 400,

"message": "Invalid value at 'contents[0].parts[1].inline_data.data' (TYPE_BYTES), Base64 decoding failed for \"'$(base64 -w0 null)'\"",

"status": "INVALID_ARGUMENT",

"details": [

{

"@type": "type.googleapis.com/google.rpc.BadRequest",

"fieldViolations": [

{

"field": "contents[0].parts[1].inline_data.data",

"description": "Invalid value at 'contents[0].parts[1].inline_data.data' (TYPE_BYTES), Base64 decoding failed for \"'$(base64 -w0 null)'\""

}

]

}

]

}

}

Finally I created a custom action which could fetch the image over URL and then convert it to base64. But now I am not getting any response from Gemini (possibly due to this faulty code that I might have written):

// Automatic FlutterFlow imports

import '/backend/backend.dart';

import '/flutter_flow/flutter_flow_theme.dart';

import '/flutter_flow/flutter_flow_util.dart';

import '/custom_code/actions/index.dart'; // Imports other custom actions

import '/flutter_flow/custom_functions.dart'; // Imports custom functions

import 'package:flutter/material.dart';

// Begin custom action code

// DO NOT REMOVE OR MODIFY THE CODE ABOVE!

import 'package:http/http.dart' as http;

import 'dart:convert';

Future<String> getImageBase64(String url) async {

http.Response response = await http.get(Uri.parse('$url'));

print(response.bodyBytes);

print("\n");

print(response);

String base64 = base64Encode(response.bodyBytes);

return base64;

}

// Set your action name, define your arguments and return parameter,

// and then add the boilerplate code using the green button on the right!

I request you to help me on urgent basis. Thanks and regards.