Broken build

[fvacek]

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Building the master, I've experienced following error

[~/t/pinetime/pinetime-rust-mynewt]$ scripts/build-app.sh                                                                                                                              [broken-build-fixed] 
+ mynewt_build_app=nrf52_my_sensor
+ rust_build_target=thumbv7em-none-eabihf
+ launch_config=launch-nrf52-pi.json
+ set +x

----- Building Rust app and Mynewt OS for thumbv7em-none-eabihf / nrf52_my_sensor...

----- Build Rust app
+ cargo build --target thumbv7em-none-eabihf
    Updating crates.io index
   Compiling app v2.1.1 (/home/fanda/t/pinetime/pinetime-rust-mynewt/rust/app)
error: proc macro panicked
   --> rust/app/src/app_network.rs:98:20
    |
98  |       let _payload = coap!( @json {        
    |  ____________________^
99  | |         //  Create `values` as an array of items under the root.
100 | |         //  Assume `val` contains `key: "t", val: 2870, geo: { lat, long }`. 
101 | |         //  Append to the `values` array the Sensor Key, Value and optional Geolocation:
...   |
107 | |         "device": &device_id,
108 | |     });
    | |______^
    |
    = help: message: index out of bounds: the len is 1 but the index is 1
    = note: this error originates in the macro `$crate::json_rep_set_text_string` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `app` due to 2 previous errors

When I change @json to @cbor build finishes with success, but the app might be broken.