MySQL client library asserts when a BLOB colum contains only NULL values

The problem is in the QMYSQLResultPrivate::bindBlobs() method. It will set the buffer_length property of the MYSQL_BIND structure to 0 because the fieldInfo reports a max_length of 0 for the "description" column (as only a NULL value is in the database).

This will cause MySQL to assert with

Assertion failed: (param->buffer_length != 0), function
setup_one_fetch_function, file libmysql.c, line 4358.