SIGSEGV on pgup/dn press

**Describe the bug**
Crashes when pressing PgUp or PgDn

**To Reproduce**
Steps to reproduce the behavior:

1. Press `3` to focus Dependencies
2. Press PgDn or PgUp

**Expected behavior**
Appropriate scroll of list

**Actual Result**
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xdc pc=0x14c1d50]

goroutine 1 [running]:
github.com/jesseduffield/lazynpm/pkg/gui.(*Gui).scrollDownView(0xc000225ae0, 0xc0001be120, 0x5c, 0x1a37801, 0xc0001bd020)
/home/runner/work/lazynpm/lazynpm/pkg/gui/global_handlers.go:41 +0x50
github.com/jesseduffield/lazynpm/pkg/gui.(*Gui).scrollDownMain(0xc000225ae0, 0xc000314000, 0xc00000a960, 0x11c6126, 0x16ce440)
/home/runner/work/lazynpm/lazynpm/pkg/gui/global_handlers.go:84 +0x53
github.com/jesseduffield/gocui.(*Gui).execKeybinding(0xc000314000, 0xc00000a960, 0xc00007a1e0, 0x2, 0xc0005e3b74, 0x2)
/home/runner/work/lazynpm/lazynpm/vendor/github.com/jesseduffield/gocui/gui.go:936 +0x93
github.com/jesseduffield/gocui.(*Gui).execKeybindings(0xc000314000, 0xc00000a960, 0xc0005e3bd0, 0x0, 0xc0001bd008, 0xc0005e3b74)
/home/runner/work/lazynpm/lazynpm/vendor/github.com/jesseduffield/gocui/gui.go:928 +0x1fa
github.com/jesseduffield/gocui.(*Gui).onKey(0xc000314000, 0xc0005e3bd0, 0x2, 0x0)
/home/runner/work/lazynpm/lazynpm/vendor/github.com/jesseduffield/gocui/gui.go:833 +0x296
github.com/jesseduffield/gocui.(*Gui).handleEvent(...)
/home/runner/work/lazynpm/lazynpm/vendor/github.com/jesseduffield/gocui/gui.go:514
github.com/jesseduffield/gocui.(*Gui).MainLoop(0xc000314000, 0xc000000003, 0xc00018fd30)
/home/runner/work/lazynpm/lazynpm/vendor/github.com/jesseduffield/gocui/gui.go:474 +0x1f2
github.com/jesseduffield/lazynpm/pkg/gui.(*Gui).Run(0xc000225ae0, 0x0, 0x0)
/home/runner/work/lazynpm/lazynpm/pkg/gui/gui.go:236 +0x853
github.com/jesseduffield/lazynpm/pkg/gui.(*Gui).RunWithSubprocesses(0xc000225ae0, 0xc0000b6d00, 0xc0000b3ec0)
/home/runner/work/lazynpm/lazynpm/pkg/gui/gui.go:280 +0x2f
github.com/jesseduffield/lazynpm/pkg/app.(*App).Run(...)
/home/runner/work/lazynpm/lazynpm/pkg/app/app.go:120
main.main()
/home/runner/work/lazynpm/lazynpm/main.go:63 +0x6e4

**Desktop (please complete the following information):**

- OS: MacOS 14.5
- Lazynpm Version v0.1.4

**Additional context**
I've tried on a handful of repos. Does seem to matter if list is too short to scroll, or plenty long and needs to scroll. I've also quickly tested while the other left hand lists are focused. It seems to crash on pgup/pgdn in all situations.