Failed to catch and interpret an error code during a scenario test

[jmhw0123]

Scenario #48: 43-add-currently-playing-to-library
Received pre-parsed assistant command
Handler thingtalk reports STOP
Handler com.bing reports NONCONFIDENT_IN_DOMAIN_COMMAND
Received ThingTalk program
Handler thingtalk reports CONFIDENT_IN_DOMAIN_COMMAND
Handler com.bing reports NONCONFIDENT_IN_DOMAIN_COMMAND
Failed to invoke query Error
    at throwError (/home/travis/build/stanford-oval/thingpedia-common-devices/main/com.spotify/index.js:61:9346)
    at SpotifyDevice.get_get_currently_playing (/home/travis/build/stanford-oval/thingpedia-common-devices/main/com.spotify/index.js:52:3294)
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async /home/travis/build/stanford-oval/thingpedia-common-devices/node_modules/genie-toolkit/dist/lib/engine/apps/exec_wrapper.js:180:65
    at async ExecWrapper.invokeQuery (/home/travis/build/stanford-oval/thingpedia-common-devices/node_modules/genie-toolkit/dist/lib/engine/apps/exec_wrapper.js:187:26)
    at async eval (eval at compile (/home/travis/build/stanford-oval/thingpedia-common-devices/node_modules/thingtalk/dist/compiler/jsir.js:792:46), <anonymous>:25:25)
    at async RuleExecutor._ruleThread (/home/travis/build/stanford-oval/thingpedia-common-devices/node_modules/genie-toolkit/dist/lib/engine/apps/rule_executor.js:61:13) {
  code: 'no_song_playing'
}
Execution state:
$dialogue @org.thingpedia.dialogue.transaction.execute;
@org.thingpedia.media-source(id="com.spotify-..."^^tt:device_id("Spotify Account of gcampax_testuser")).get_currently_playing() => @com.spotify(id="com.spotify-..."^^tt:device_id("Spotify Account of gcampax_testuser")).add_item_to_library(playable=id)
#[results=[]]
#[error=enum no_song_playing];
Genie executed new program: uuid-d851f120-5068-4b66-96f8-a9f9b44633fb
  stats: size(charts[0][ctx_completed_action_error]) = 1
  stats: size(charts[0][sorry_preamble]) = 1
   stats: size(charts[1][short_action_error_message]) = 1
  stats: size(charts[2][action_error_phrase]) = 1
 stats: size(charts[3][$agent]) = 1
Agent act:
$dialogue @org.thingpedia.dialogue.transaction.sys_action_error;
Genie says: Sorry, there was an unexpected error with your command. Please try again later or report this issue to my developers.
Invalid reply: Sorry, there was an unexpected error with your command. Please try again later or report this issue to my developers.
>> expecting = null
Expected:  /(Sorry, no item is currently playing\.|I added an item to your library.)\n>> expecting = null/