fix(设备详情): 修复呼吸率数据为空时图表显示undefined的问题

当呼吸率数据为空时清空数组，避免图表显示错误
添加数据长度检查防止未定义错误

src/views/device/detail/components/breathLineChart/index.vue

@@ -90,6 +90,7 @@ onMounted(() => {
 watch(
   () => props.data,
   (newData) => {
+    console.log('🚀🚀🚀 newData', newData)
     const list = newData
     if (list.length > 60) {
       list.shift()
@@ -102,7 +103,7 @@ watch(
               ? [{ ...option.value.series[0], data: list }]
               : [{ ...option.value.series, data: list }]
             : [{ data: list }], // 更新折线数据
-        title: [{}, { text: `BPM: ${newData[newData.length - 1]} 次/分钟` }, {}], // 更新实时BPM
+        title: [{}, { text: `BPM: ${list && list.length && list[list.length - 1]} 次/分钟` }, {}], // 更新实时BPM
       },
       { notMerge: false }
     )
@@ -111,7 +112,7 @@ watch(
 )
 </script>
 
-<style scoped>
+<style scoped lang="less">
 .chart {
   width: 100%;
   height: 300px;

src/views/device/detail/index.vue

@@ -395,6 +395,8 @@ onMounted(() => {
       const breathRpm = data.health?.breath_rpm || 0 // 呼吸率数据
       if (breathRpm) {
         breathRpmList.value.push(Math.floor(breathRpm || 0))
+      } else {
+        breathRpmList.value = []
       }
       console.log(`🚀 收到MQTT消息 ${formatDateTime(new Date())}`, {
         '🔴 目标人数': arr.length,