Keyboard keys initialized with 'undefined' type - not liked by browser

Hello,
I am getting an undefined keyboard keys error (both for keySendResponse.keys and keyMoveCursor.keys) while running my project test2.js on Pavlovia.

The link to my project is https://gitlab.pavlovia.org/OLeticevscaia/wm-protection.
The keyboards themselves are defined in lines 188 and 190.
Then in the function recallRoutineBegin, keySendResponse.keys and keyMoveCursor.keys are initialized with ‘undefined’ type (lines 756 and 759).
Each frame, I use the keyMoveCursor keys to move an image stimulus on the screen (recallRoutineEachFrame function). The main condition I use is the length of the key list. So when I am checking the length for the first frame - the keys are of undefined type (line 867) and an exception is thrown.
As a workaround, I tried to replace undefined with an empty list (and the corresponding emptiness conditions in the recallRoutineEnd function) - but it seems to change the behaviour.

Could you please advice me how can I fix this issue?

Thank you in advance!

Olga