NVUE为什么固定在底部后，justify-content: center无效

<template>  
    <view>  
        <view class="tabbar-background">  
            <view class="scan-background"></view>  
        </view>  
    </view>  
</template>  

<script>  
    export default {  

    }  
</script>  

<style>  
    .tabbar-background {  
        /* #ifndef APP-PLUS-NVUE */  
        display: flex;  
        box-sizing: border-box;  
        /* #endif */  
        flex-direction: row;  
        justify-content: center;  
    }  

    .scan-background {  
        /* #ifndef APP-PLUS-NVUE */  
        display: flex;  
        box-sizing: border-box;  
        /* #endif */  
        width: 120rpx;  
        height: 120rpx;  
        border-radius: 50%;  
        box-shadow: 0px -3px 10px 0px rgba(204, 204, 204, 0.5);  
    }  
</style>  

以上样式只要改为
.tabbar-background {
/ #ifndef APP-PLUS-NVUE /
display: flex;
box-sizing: border-box;
/ #endif /
flex-direction: row;
justify-content: center;
position: fixed;
bottom: 0;
}
scan-background 就不会居中了