Review code for use of expect()/unwrap()/panic!()/assert!()

[simongdavies]

There are numerous places where we use either expect()/unwrap()/panic!()/assert!() we should review and remove these where possible as they will cause the host process to crash.

Consider adding the following clippy checks:

expect_used
panic
unwrap_used

We should also check for use of indexing like this function_call.parameters.clone().unwrap()[0].clone() without checking the number of items.