fix(规则管理): 修复自定义表格组件中行合并逻辑的空引用问题

src/views/rulesManagement/releaseRules/components/templateDiv/customTable.vue

@@ -166,7 +166,7 @@
         } else {
           this.columns.forEach((item, index) => {
             let _rowIndex = rowIndex;
-            if (item[rowIndex].rowspan > 1) {
+            if (item[rowIndex]?.rowspan > 1) {
               _rowIndex += Number(item[rowIndex].rowspan);
             }
             this.columns[index].splice(_rowIndex + 1, 0, {