I use #if in Svlte Native but it doesn't work

Question

I try out Svelte Native and I try to hide "tags" with booleans. I try this, which works in the normal Svelte framework like:

{#if po.id !== null || po.id !== undefined}
        <flexboxLayout flexWrap="wrap" class="v-a-c t-a-c" >
            <label text="first" width="70%" backgroundColor="#63c3d0" class="m6"></label>
            <label text="second" width="70%" backgroundColor="#63c3d0" class="m6"></label>
            <label text="third" width="70%" backgroundColor="#63c3d0" class="m6"></label>
        </flexboxLayout>
    {:else }
        <stackLayout flexWrap="wrap" class="v-a-c t-a-c">
            <textField  bind:text="{personName}" class="m6 new-person" ></textField>
            <button text="add new value" on:tap="{createNewPlayer}" />
        </stackLayout>
    {/if}

So why it doesn't work? What am I doing wrong?