"Loki" example does not compile

[apiraino]

The Loki example does not compile.

$ cargo run help
   Compiling test-thunder v0.1.0 (/home/xxx/tmp/test-thunder)
error: custom attribute panicked
 --> src/main.rs:9:1
  |
9 | #[thunderclap(example: Option<String>: "Error, here", another_example: String: "No error, here")]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: message: index out of bounds: the len is 1 but the index is 1

Running on edition = "2018":

$ rustc --version
rustc 1.33.0-nightly (adbfec229 2018-12-17)