HarmonyOS RichEditor实现超过文字字数删除功能，发现删除功能失效

// 输入框文字校验  
inputNumCheck(){  
  this.controllerRich.getSpans({  
    start: this.start,  
    end: this.end}).forEach(item => {  
    if (typeof (item as RichEditorImageSpanResult)['imageStyle'] !== 'undefined') {  
      this.inputNum++  
    } else {  
      this.inputNum = (item as RichEditorTextSpanResult).value.length;  
    }  
  })  
}  
build() {  
  Column() {  
    Row(){  
      // 输入框  
      RichEditor({ controller: this.controllerRich})  
        .height($r('app.integer.chat_with_expression_chat_input_height'))  
        .layoutWeight(LAYOUT_WEIGHT)  
        .borderRadius($r('app.integer.chat_with_expression_chat_border_radius'))  
        .backgroundColor($r('app.string.chat_with_expression_input_background'))  
        .margin({ top: $r('app.integer.chat_with_expression_express_margin_top') ,left:14})  
        .key(this.focusKey)  
        .id(this.focusKey)  
        .placeholder('平台提倡文明用语，请温柔发言哦~',{font:{size:12},fontColor:'#999999'})  
        .defaultFocus(true)  
        .aboutToIMEInput((value: RichEditorInsertValue)=>{  
          if (this.inputNum >= 50) {  
            // 输入字符数超过50个 就禁止输入  
            try {  
              promptAction.showToast({  
                message: '最多只能输入50个汉字哦',  
                duration: 2000  
              });  
            } catch (error) {  
              let message = (error as BusinessError).message  
              let code = (error as BusinessError).code  
              console.error(`showToast args error code is ${code}, message is ${message}`);  
            };  
            return false  
          } else {  
            this.inputNumCheck()  
          }  
          return true  
        })