Leaving cells with default values "empty" does not work in Spreadsheet editor.

**Describe the bug and expected behavior**

**To Reproduce (please include link if applicable)**
Steps to reproduce the behavior:
Create following table:

``` sql
CREATE TABLE tbl_test (
guid binary(16) NOT NULL DEFAULT (UUID_TO_BIN(UUID())),
name varchar(50) NOT NULL,
PRIMARY KEY (guid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin
```
Open Spreadsheet editor and leave guid empty. It will throw an error. (Inserting with script works.)

**Screenshots**