originalFetch is not a function

### Expected Behaviour

### Actual Behaviour

### Reproduce Scenario (including but not limited to)

#### Steps to Reproduce
const proxyFetch = createFetch();

const aemHeadlessClient = new AEMHeadless({
serviceURL: ' ',
endpoint: '/content/_cq_graphql/global/endpoint.json',
fetch: proxyFetch,
headers: {'content-type': 'application/json', 'accept': 'application/json'},
// auth: ['admin', 'admin'],
//auth: [AEM_USER, AEM_PASS],
// headers: {'customerheadername': 'customerheadervalue'}
});
aemHeadlessClient.runQuery(`query homePageQueery {
homepageFragmentList {
items {
_path
title
}
}
}`)
.then(data =>

console.log(data))
.catch(e =>
console.error(e))
#### Platform and Version

#### Sample Code that illustrates the problem

#### Logs taken while reproducing problem
AioCoreSDKError [AEMHeadlessError]: [AEMHeadless:REQUEST_ERROR] General Request error: originalFetch is not a function.
code: 'REQUEST_ERROR',
sdk: 'AEMHeadless',

Start with the createFetch() value passed to AEMHeadless and the request path used by runQuery; inspect how the SDK invokes the custom fetch. Reproduce the reported “originalFetch is not a function” error and confirm the request completes with the supplied proxy fetch.

Written by the indexing model from the issue text.