[BUG] Too many plots blows up layout

[BioTurboNick]

ps = map(1:9) do _
	areaplot(1:1000, rand(1000))
end
plot(ps..., layout = grid(9, 1))

ps = map(1:10) do _
	areaplot(1:1000, rand(1000))
end
plot(ps..., layout = grid(10, 1))

Affects GR at least.

Thinking about automatically extending the size of the plot as in #4234 may be relevant here. Or need a way to fail more gracefully.