Cannot read property 'executeQuery' of null

[ruban258]

Hi all,
Can anybody help me understand why i'm getting this error:

My setup :

New sveltekit project.

error msg:
Cannot read property 'executeQuery' of null TypeError: Cannot read property 'executeQuery' of null at C:\Repos\AGScada\node_modules\@urql\svelte\dist\urql-svelte.js:234:11 at C:\Repos\AGScada\node_modules\wonka\dist\wonka.js:254:18 at Object.next (C:\Repos\AGScada\node_modules\wonka\dist\wonka.js:1161:14) at C:\Repos\AGScada\node_modules\@urql\svelte\dist\urql-svelte.js:173:11 at Object.subscribe (C:\Repos\AGScada\node_modules\svelte\store\index.js:53:9) at Object.subscribe (C:\Repos\AGScada\node_modules\@urql\svelte\dist\urql-svelte.js:96:14) at C:\Repos\AGScada\node_modules\@urql\svelte\dist\urql-svelte.js:168:14 at C:\Repos\AGScada\node_modules\wonka\dist\wonka.js:1159:9 at C:\Repos\AGScada\node_modules\wonka\dist\wonka.js:247:7 at C:\Repos\AGScada\node_modules\wonka\dist\wonka.js:590:18

Source Code index.svelte:

    import { setClient, query, operationStore, subscription } from '@urql/svelte';
    import { createClient, defaultExchanges, subscriptionExchange } from '@urql/svelte';
    import { createClient as createWSClient } from 'graphql-ws';
    const wsClient = process.browser ? createWSClient({url: 'ws://localhost:5000/graphql',}):null;  
    const client = process.browser ? createClient({
    url: 'http://localhost:5000/graphql',
    exchanges: [
      ...defaultExchanges,
      subscriptionExchange({
        forwardSubscription: (operation) => ({
          subscribe: (sink) => ({
            unsubscribe: wsClient.subscribe(operation, sink),
          }),
        }),
      }),
    ],
  }): null;

    let tags = operationStore(`query {tags{tagName value}}`);

    let onTagUpdated = operationStore(`subscription {onTagUpdated{tagName value}}`);

    query(tags);
    subscription(onTagUpdated);

    setClient(client);

    if($tags.fetching)
    {
        console.log("loading");
    }    
    else
    {
        console.log($tags.data);
    }

Thankyou for any help.