This fix is a follow up on the fix for similar issue 56761.

When sanitizing data read from the events_waits_history_long table,
the code needs also to sanitize the schema_name / object_name / file_name pointers,
because such pointers could also hold invalid values.
Checking the string length alone was required but not sufficient.

This fix verifies that:
- the table schema and table name used in table io events
- the file name used in file io events
are valid pointers before dereferencing these pointers.