[VolumeScroll] spoon does not work.

The [VolumeScroll spoon](https://www.hammerspoon.org/Spoons/VolumeScroll.html) has several problems:
- **When started via `spoon.VolumeScroll.start()`**
- `*** ERROR: .../leftium/.hammerspoon/Spoons/VolumeScroll.spoon/init.lua:64: attempt to index a nil value (local 'self')`
- **Starting this way works: `spoon.VolumeScroll.start({ "cmd", "alt"})`** But now on mouse scroll:
- `ERROR: LuaSkin: hs.eventtap callback error: .../leftium/.hammerspoon/Spoons/VolumeScroll.spoon/init.lua:49: attempt to call a nil value (method 'sameMods')`
- **So I removed all the checks for modifiers to see how the volume control part works...**
- The volume control works for a while, but the event tap eventually just stops getting events.
- Also the volume control felt "mushy." I think 1% volume steps feel too small?

---

**Detailed steps:**
1. Downloaded VolumeScroll.spoon.zip from https://www.hammerspoon.org/Spoons/VolumeScroll.html
2. Extracted zip file; double-clicked VolumeScroll.spoon to install.
3. Added these lines to my ~/.hammerspoon/init.lua:

```
hs.loadSpoon("VolumeScroll")
spoon.VolumeScroll.start({ "cmd", "alt"})
```

**Environment:**
- MacOS 15.5 (24F74)
- Hammerspoon version 1.0.0 (6864)