Builtin: Sanity-check /time inputs (minetest#11993)

This enforces the documented bounds for the /time command.

builtin/game/chat.lua

@@ -1034,12 +1034,11 @@ core.register_chatcommand("time", {
  end
  local hour, minute = param:match("^(%d+):(%d+)$")
  if not hour then
- local new_time = tonumber(param)
- if not new_time then
- return false, S("Invalid time.")
+ local new_time = tonumber(param) or -1
+ if new_time ~= new_time or new_time < 0 or new_time > 24000 then
+ return false, S("Invalid time (must be between 0 and 24000).")
  end
- -- Backward compatibility.
- core.set_timeofday((new_time % 24000) / 24000)
+ core.set_timeofday(new_time / 24000)
  core.log("action", name .. " sets time to " .. new_time)
  return true, S("Time of day changed.")
  end