<<numberslider>> in the numberpool addon breaks on example use case, variable undefined

[Robert-Lloyd3]

Describe the bug.

The <<numberslider>> macro in the numberpool addon for SugarCube v2 (listed on The SugarCube v2 home page) fails when provided with the example usage case from the included numberpool documentation on latest Chrome-based browsers. Other browsers have not been tested to see if the issue reproduces.

<<numberslider "$opacity" $opacity 0 1 0.5>>

To Reproduce:
Steps to reproduce the behavior:

1. In Twine, create a new Story
2. Install the numberpool addon per instructions
3. Add the following to the default start passage

<<set $opacity to 0.5>>
<<numberslider "$opacity" $opacity 0 1 0.5>>

5. Click on Build, then Play
6. A wild error message appears
   Error: cannot execute macro <<numberslider>>: Cannot read properties of undefined (reading 'hasOwnProperty')

Expected behavior.
A horizontal slider from 0 to 1 with half-step increments is expected to be displayed.

Screenshots.

• None.

Project details.

• SugarCube Version: 2.37.3
• Included Add-ons: numberpool
• Included Libraries: None
• Compiler & Version: Twine 2.10.0

Desktop details.

• Windows 11
• Chrome 131.0.6778.205 (Official Build) (64-bit)
• Edge 131.0.2903.112 (Official build) (64-bit)

Smartphone/tablet details.

• Not tested

Additional context.
To fix this issue, replace the following lines

return null !== parent && parent.hasOwnProperty("pool") ? parent.pool : null

with:

return undefined !== parent && null !== parent && parent.hasOwnProperty("pool") ? parent.pool : null

I'd submit the fix, but I have been unable to find the repo for it.

Thanks.