protect against decimals in menu/tape.lua

[dndrks]

from https://llllllll.co/t/tape-isnt-recording/64461/10

re:

norns/lua/core/menu/tape.lua

Lines 56 to 61 in e8e210a

	for f in tape:gmatch("([^\n]+)") do
	fs = string.sub(f,1,4)
	if tonumber(fs) then
	table.insert(t,tonumber(fs))
	end
	end

if a file in audio/tape is named something like 10.20.24.wav, then it'll be string.sub'd as index 10.2 which passes the tonumber check and gets assumed as m.fileindex. but, later on, this string.format fails, since 10.2 doesn't have an integer representation and then the entire TAPE record process fails to initiate.

a more robust fix would add tapeindex to the norns.state table for iteration, removing the need for this checking, but this modulo check seems like the least invasive option. happy to spin up in the other direction, though!