Forms :: Two Blocks - Unable To INSERT Record

I have this error. To put it simply I have two blocks.

Block1 contains two drop down list with PL/SQL statements for queries.
Block2 contains tabular form created from block wizard (I tried already in manual)

that will catch the result in Block1 queries.

Now I have a button with a trigger when-button-pressed that contains

BEGIN
INSERT INTO dummy1
VALUES ('hello',1,2,3);
COMMIT;
END;

My goal is to add into dummy1 values from :block2.item_name1, :block2.item_name2, :block2.item_name3 but to put it simply I tried these values but I received the same error.

When I run it and first things first click the button, the values will be added into dummy1 table but when I execute the block1 - dropdown list queries and try to press the button. I received the error.