fix(wms): 修复重量输入框精度问题并统一初始化值

将重量输入框的精度设置为3位小数，确保数据一致性
将null初始化值改为undefined，避免潜在的类型问题

klp-ui/src/views/wms/coil/split.vue

@@ -156,13 +156,13 @@
                 </el-form-item>
 
                 <el-form-item label="毛重(t)" required>
-                  <el-input-number :controls="false" v-model="item.grossWeight" placeholder="请输入毛重" type="number" step="0.01"
+                  <el-input-number precision="3" :controls="false" v-model="item.grossWeight" placeholder="请输入毛重" type="number" step="0.01"
                     :disabled="readonly">
                     <template slot="append">吨</template>
                   </el-input-number>
                 </el-form-item>
                 <el-form-item label="净重(t)" required>
-                  <el-input-number :controls="false" v-model="item.netWeight" placeholder="请输入净重" type="number" step="0.01"
+                  <el-input-number precision="3" :controls="false" v-model="item.netWeight" placeholder="请输入净重" type="number" step="0.01"
                     :disabled="readonly">
                     <template slot="append">吨</template>
                   </el-input-number>
@@ -255,11 +255,11 @@ export default {
           materialType: null,
           itemType: null,
           itemId: null,
-          grossWeight: null,
-          netWeight: null,
+          grossWeight: undefined,
+          netWeight: undefined,
           warehouseId: null,
           actualWarehouseId: null,
-          length: null,
+          length: undefined,
         }
       ],
       loading: false,