"Serialisation of timeline item failed." when pushing timeline pins

[alni]

Hi.

When i try to push timeline pins with PebbleKit JavaScript to the emulator I get this error message in the log "Serialisation of timeline item failed.", but the response from the Pebble timeline API backend returns "OK"

During my searching after solutions i found that the "Serialisation of timeline item failed." message is defined in the https://github.com/pebble/pypkjs project, but I am not sure if the error was due to the emulator in CloudPebble or the pypkjs project directly.

This happens with both the Aplite and the Basalt emulators.