panic: runtime error: slice bounds out of range [808:773]

[cbeuw]

This panic happens when using the slicer toxic:

panic: runtime error: slice bounds out of range [808:773]

goroutine 114 [running]:
github.com/Shopify/toxiproxy/v2/toxics.(*SlicerToxic).Pipe(0x1400020c0f0, 0x1400021e480)
	github.com/Shopify/toxiproxy/v2/toxics/slicer.go:65 +0x320
github.com/Shopify/toxiproxy/v2/toxics.(*ToxicStub).Run(0x1400021e480, 0x14000210d20)
	github.com/Shopify/toxiproxy/v2/toxics/toxic.go:86 +0xb8
created by github.com/Shopify/toxiproxy/v2.(*ToxicLink).Start in goroutine 58
	github.com/Shopify/toxiproxy/v2/link.go:109 +0x2c8

The bug is here: https://github.com/Shopify/toxiproxy/blob/7abcb6f9cf95d2fb27244435e22b16bda14ab5c3/toxics/slicer.go#L42-L44

rand.Intn can return a number in [0, SizeVariation*2), so it can be less than SizeVariation, resulting a negative RHS and a mid less than start