fix: 【桌面版】优化excel导入与web端显示一致

core/core-backend/src/main/java/io/dataease/datasource/provider/H2EngineProvider.java

@@ -56,7 +56,7 @@ public class H2EngineProvider extends EngineProvider {
             values.append("('").append(String.join("','", Arrays.asList(strings1)))
                     .append("'),");
         }
-        return (insertSql + values.substring(0, values.length() - 1));
+        return (insertSql + values.substring(0, values.length() - 1)).replaceAll("'null'", "null");
     }