tables can cause server to crash!

The bug will be fixed by patch for #34779: "crash in checksum table
on federated tables with blobs containing nulls"

Only a test case commited.


mysql-test/r/federated.result:
  Test case for bug #34774: key prefix on text field in federated 
  tables can cause server to crash!
    - test result.
mysql-test/t/federated.test:
  Test case for bug #34774: key prefix on text field in federated 
  tables can cause server to crash!
    - test case.