I created one table:
CREATE TABLE "test2" ("value" character varying(256) NOT NULL UNIQUE PRIMARY KEY,"tester" integer,"testing" integer);
and I tried to insert values and I clicked GO without entering any value. Instead of getting a message such as "value" field cannot be empty, I got the CUBRID semantic error displayed. I understand what it means, but new users might not.
I think the correct approach is not allowing to click "GO" unless you have at least 1 column value entered. A proper error should be displayed such as no values entered.