fix: 电子围栏不存在时，不显示‘‘检测围栏外部’’和‘前台画面显示’

src/views/cameras/algo-params-setting/components/FenceToolbar/FenceToolbar.vue

@@ -13,26 +13,27 @@
       {{ selectedAlgoDetail?.algoInfo?.name }}
     </div>
     <PresetSelect />
-
-    <div style="display: flex">
-      <ElCheckbox label="检测围栏外部" v-model="isFenceRegionOut" @update:modelValue="handleUpdateRegion" />
-      <ElCheckbox label="前台画面显示" v-model="isDisplayFenceInVideo" @update:modelValue="handleUpdateDisplay" />
-      <a :href="previewUrl" target="_blank" style="margin-left: 20px" v-if="previewUrl && false">平台相机预览</a>
-    </div>
-    <div class="fenceListWrapper">
-      <FenceNameItem
-        :active="item.id === fenceStore.currentFenceId"
-        v-for="item in fenceStore.allFences"
-        :detail="item"
-        :key="item.id"
-        @click="handleSelectFence(item.id)"
-        @delete="handleDeleteFence"
-        @edit="handleEditFenceInfo(item)"
-      />
-    </div>
-    <div v-if="fenceStore.allFences.length > 0" style="text-align: right">
-      <ElButton size="small" @click="handleCancelFence">取消</ElButton>
-      <ElButton type="primary" size="small" @click="handleSaveFence">保存</ElButton>
+    <div v-if="fenceStore.allFences.length > 0">
+      <div style="display: flex">
+        <ElCheckbox label="检测围栏外部" v-model="isFenceRegionOut" @update:modelValue="handleUpdateRegion" />
+        <ElCheckbox label="前台画面显示" v-model="isDisplayFenceInVideo" @update:modelValue="handleUpdateDisplay" />
+        <a :href="previewUrl" target="_blank" style="margin-left: 20px" v-if="previewUrl && false">平台相机预览</a>
+      </div>
+      <div class="fenceListWrapper">
+        <FenceNameItem
+          :active="item.id === fenceStore.currentFenceId"
+          v-for="item in fenceStore.allFences"
+          :detail="item"
+          :key="item.id"
+          @click="handleSelectFence(item.id)"
+          @delete="handleDeleteFence"
+          @edit="handleEditFenceInfo(item)"
+        />
+      </div>
+      <div style="text-align: right">
+        <ElButton size="small" @click="handleCancelFence">取消</ElButton>
+        <ElButton type="primary" size="small" @click="handleSaveFence">保存</ElButton>
+      </div>
     </div>
     <div>
       <EditFenceDialog