Submitted by: @hvlad

In the case below the internal DSQL statement is run on commit when index is modified.
Note, most internal statements used by the engine is ESQL, not DSQL - thus they are not interact with StatementTImeout.

set term ^;

execute block as begin
in autonomous transaction do
execute statement 'set statistics index rdb$index_0';
end
^
set statement timeout 60
^
execute block as begin
in autonomous transaction do
execute statement 'set statistics index rdb$index_0';
end
^

Statement failed, SQLSTATE = 08006
Error reading data from the connection.

The bug was reported by Pavel Zotov with much more complex scenario.

Commits: 1b9f5d8