plot: plots fails to render with oversized glyphs

### What are you trying to do?

Generate a box plot visualization on a canvas of a specified width and height.

### What did you do?

https://go.dev/play/p/EzwxtwaRRnA

Unfortunately, this times out while fetching gonum, so I cannot verify that it builds and runs correctly in the Go playground. However I have tested it locally with go 1.21.1 darwin/arm64. It reproduces for me against both the 0.13.0 and 0.14.0 tags.

### What did you expect to happen?

I expected both `p1.svg` and `p2.svg` to contain the generated box plots. If for some reason gonum/plot was unable to render the plot correctly with the specified dimensions, I would have expected some kind of error, rather than a nil error and an empty output.

### What actually happened?

`p1.svg` contains the expected plot, but `p2.svg` is blank, with only the axes being rendered. I will attach copies of `p1.svg` and `p2.svg` as generated on my local machine.

p1:


p2:


I also tried using PNG outputs rather than SVG, but the results were the same, so I do not believe this issue is SVG-specific.

### What version of Go and Gonum/plot are you using?

```
$ go version
go version go1.21.1 darwin/arm64
$ cat go.mod | grep gonum
require gonum.org/v1/plot v0.13.0
```

(it is also broken on 0.14.0)

### Does this issue reproduce with the current master?

I tried testing against 342a5cee2153b051d94ae813861f9436c5584de2, which shows up in go.mod as `require gonum.org/v1/plot v0.14.1-0.20230902105700-342a5cee2153` for me. The behavior was the same as what I described.

I believe this reproduces against the current master branch at time of writing.