I can not access a list element with dynamic index

[saig0]

Describe the bug
It is not possible to access a list element (i.e. via filter expression) if the index is a variable reference instead of a constant number.

["a","b","c"][2]
// "b"

["a","b","c"][index]
// failure: expected Boolean but found 'ValNumber(2)'

To Reproduce
Steps to reproduce the behavior:

1. Evaluate a filter expression ["a","b","c"][index] with context variable index = 2

Expected behavior
I can access a list element statically and dynamically with a variable reference in the same way.

Environment
Which version do you use? 1.10.0

[falko]

@saig0 Should this become a TCK test?

[saig0]

I didn't check the newest TCK tests yet. But it would make sense to have also test with non-static values :)