That's an SSR issue. The component gets rendered in the server first and it can't find the destroy property of something which only exists in the browser.

This can be solved by adding a browser guard, like so:

<script>
    import { browser } from "$app/env";
    import { JustifiedGrid } from "@egjs/svelte-grid";
  
    const gap = 5;
    const defaultDirection = "end";
    const rowRange = 0;
    const columnRange = [1,8];
    const sizeRange = [200,1000];
    const isCroppedSize = false;
    const displayedRow = -1;
</script>

{#if browser}
    <JustifiedGrid
        class="container"
        {defaultDirection}
        {gap}
        {rowRange}
        {columnRange}
        {sizeRange}
        {isCroppedSize}
        {displayedRow}
    >
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3</div>
        <div class="item">4</div>
        <div class="item">5</div>
        <div class="item">6</div>
        <div class="item">7</div>
        <div class="item">8</div>
        <div class="item">9</div>
        <div class="item">10</div>
    </JustifiedGrid>
{/if}

However, this solution is ugly and not idiomatic. The library author should probably strive to make it work with SSR (maybe you can consider contributing to said library!).