webview.setCssText不生效

onLoad(option) {
this.id = option.id
const wv = this.$scope.$getAppWebview()
if (wv) {
console.log('====设置样式0=====')
wv.setCssText('body{background: red!important}')
console.log('====设置样式1=====')
}
}

在onLoad使用setCssText动态设置样式无效，看xcode提示如下：
2022-10-13 22:05:06.852785+0800 UniPluginDemo[9658:251121] <Weex>[log]WXBridgeContext.m:1310, jsLog: ====设置样式0===== at pages/mall/goodsDetail.vue:74 LOG
2022-10-13 22:05:06.853160+0800 UniPluginDemo[9658:251121] <Weex>[log]WXBridgeContext.m:1310, jsLog: ====设置样式1===== at pages/mall/goodsDetail.vue:76 LOG
2022-10-13 22:05:06.868599+0800 UniPluginDemo[9658:250906] [Runtime][INFO:] appendPreloadCssText[(null)]
2022-10-13 22:05:06.880791+0800 UniPluginDemo[9658:251121] <Weex>[log]WXBridgeContext.m:1310, jsLog: [formatParams] format:---COMMA--- at utils/api.js:203 __LOG
2022-10-13 22:05:06.960428+0800 UniPluginDemo[9658:250906] [Runtime][DEBUG:] show NWindow--[2]
2022-10-13 22:05:07.283297+0800 UniPluginDemo[9658:250906] [Runtime][INFO:] refreshWhitePageCheckWebview---evt[3]---[<PDRCoreAppFrame: 0x7fbf0a031c00; frame = (0 0; 414 896); clipsToBounds = YES; layer = <CALayer: 0x600002744e20>>]

特别的是下面这个提示
2022-10-13 22:05:06.868599+0800 UniPluginDemo[9658:250906] [Runtime][INFO:] appendPreloadCssText[(null)]

为什么会有null呢？麻烦官方解答一下