Brief summary of issue / Description of requested feature:

I created a key binding to cycle through my available fonts, and change the font of the minimap which is comprised of monospace utf8 ascii art, so that i could find the best looking font out of what my system offers.

In the process I found if you increment the list of fonts beyond the available fonts(size of the fonts table), it will crash Mudlet.

here is the key binding script I was using at the time:

if not fontlist then
	fontlist=getAvailableFonts()
	fontindex={}
  for k,v in pairs(fontlist) do
			fontindex[#fontindex+1]=k
  end
end
fontx = fontx or 0
fontx = fontx + 1
--fontx=150
echo(fontx .. ": " .. fontindex[fontx] .. "\n")
setFont("minimap", fontindex[fontx])

Steps to reproduce the issue / Reasons for adding feature:

to reproduce try setting the font with fontindex[fontx] where fontx exceeds the boundaries of the fontindex table.

Error output / Expected result of feature

On Mudlet crash the linux console I launched it from reported: Floating point exception (core dumped)

Extra information, such as Mudlet version, operating system and ideas for how to solve / implement:

Mudlet 3.17.1-dev on Ubuntu 18.10 with KDE