perf(src/packages): 优化小组件里大标题1，清除背景置空选择框内容

@@ -130,7 +130,7 @@ const props = defineProps({
 })
 const uploadFileListRef = ref()
 
-const selectValue = ref('headerBg08.png')
+const selectValue = ref<string| null>('headerBg08.png')
 
 const getAllBackgroundImageList = computed(() => {
   const pathList = import.meta.glob('../../../../../../assets/external/headbackground/*')
@@ -220,7 +220,7 @@ const handleChange = (value: boolean) => {
 const clearImage = () => {
   props.optionData.backgroundImage = ''
   props.optionData.bgSrc = ''
-  selectValue.value = ''
+  selectValue.value = null
 }
 </script>
 <style lang="scss" scoped>