There are quite a few variables in the code that are no longer
(or perhaps never were) in use. These were discovered by enabling
compiler warnings for unused variables and cleaning them up.
In most cases where the unused variables were the result
of a function call the call was left but the variable
assignment removed, unless it was obvious that it was
a simple getter with no side effects.
(1) If the user denies something on the Ledger,
a proper error message is now shown.
(2) Ledger doesn't time out anymore while waiting
on user input.
(3) Lower the timeout to 2 seconds, this is enough for
normal Ledger <-> System communication.
