Crash for bit array pattern on JS target

[giacomocavalieri]

This code:

pub fn main() {
  case <<12:size(1)>> {
    <<1.2:float, _>> -> 1
    _ -> 2
  }
}

Throws an exception on the JavaScript target: Error: Invalid bit array slice: start = 0, end = 64, bit size = 1 . It looks like the pattern matching code doesn't check the length of the bit array is sufficient to call the bitArraySliceToFloat function

[giacomocavalieri]

This is being worked on in #4382