following issue from DBZ-7093 to cover case 4.

Case 4. Modify column type from int to varchar

modified column data was sent to topic with NULL with unexpected value warning log.

Unexpected value for JDBC type 4 and column col4 INT DEFAULT VALUE NULL: class=byte[] (io.debezium.connector.mysql.MySqlValueConverters)  

throw an error? No, but there is warning log.

is there a risk of data corruption? Yes, modified column value is NULL