TypeError: Cannot read property 'toString' of null

[Romanevigano]

URL of experiment: exp [PsychoPy]

Description of the problem:
Hello, when I try to run my experiment on pavlovia this error message appears. Could someone help me please?

Error message :
" Error

Unfortunately we encountered the following error:

TypeError: Cannot read property ‘toString’ of null

Try to run the experiment again. If the error persists, contact the experiment designer. "

[wakecarter]

You put null in your slider labels. Try just putting two labels.

You might also find my interactive slider demo useful.

PsychoPy Online Demos

If you have routines or experiments that are likely to be useful to others, please create a post in this thread, editing your post to add new demos so there is one post per creator. Ideally set your demos so they can be tested without consuming a credit (if you don’t have a site license) by adding a final routine that can’t end, disabling save incomplete results and adding a small number of credits. Please do not discuss the demos in this thread or create more than one post unless you have a la…

[Romanevigano]

Thank you for your answer. I changed this but now another error message appears:

it must come from the position on the plane file because it is equal to (0.4,0).
So what should we do?

[wakecarter]

Are you sure you’ve uploaded the correct error message there?

Have a look for the offending line via the Browser Console.

Use Ctrl-Shift-R to refresh if you are running the old code.

[Romanevigano]

oops no you’re right I put the old error message, I’m sorry!
Here is the correct message:

[Romanevigano]

here is an overview of my external list:

[wakecarter]

You could try square brackets.

Alternatively, if your Y coordinate is always 0 you could just put 0.4 / -0.4 and the use the position $[PositionA,0]

Personally, I would use 1 and -1 so I can easily adjust the final position, e.g. $[.4*PositionA,0]