【报Bug】uniapp里的webview加载无title的网页时，导航栏返回键 会消失

示例代码：

template：

<template>  
    <view class="view view-border-top-default">  
        <view class="view-body">  
            <web-view  
                class="webview"  
                @onPostMessage="handPostMessage"  
                :style="{ bottom: bottom }"  
                :webview-styles="webviewStyles"  
                style="width: 100%;"  
                :src="webviewURL"  
            ></web-view>  
        </view>  
    </view>  
</template>  

script：

onLoad(option) {  
        // console.log('@option:', option)  

        if (option.title) {  
            uni.setNavigationBarTitle({  
                title: decodeURIComponent(option.title)  
            });  
        }  
        if (option.url) {  
            let userAgent = plus.navigator.getUserAgent()  
            userAgent = userAgent+' anjuleye/10.0'  
            if(option.modifyUserAgent){  
                userAgent = userAgent.replace('uni-app', 'uniapp')  
            }  
            plus.navigator.setUserAgent(userAgent)  
            this.webviewURL = 'https://mp.weixin.qq.com/s?__biz=MzI4NzE4ODgwOA==&mid=504688560&idx=1&sn=98c9c64832d40e7bb8d8db2efa94e2da&chksm=70313d974746b481a776554ca684423672c66690375c3696a9104a15972f9ea841c8396fba42#rd'           
            this.wvTimer = setTimeout(() => {  
                const currentWebview = this.$scope.$getAppWebview();  
                this.wv = currentWebview && currentWebview.children()[0];  
                this.wvTimer = null  
            }, 1000);  
        }  
        if (uni.getSystemInfoSync().platform === 'android') {  
            uni.onKeyboardHeightChange(res => {  
                console.log('onKeyboardHeightChange', res.height);  
                this.bottom = res.height;  
            });  
        }  
    },  

操作步骤：

打开无title的网页url

预期结果：

导航栏可以返回

实际结果：

导航栏返回键消失