Segmentation fault when using upower and playerctl interfaces

Hello lgi development team. I've encounteded an issue with both lua and luajit when trying to use the playerctl and upower interfaces. The output itself is not very descriptive as the command line only reads `Segmentation fault".

I don't even know where to start as it is easy to get lost, I've made the following upower example code to explain:

local upower = require("lgi").require("UPowerGlib")
local devices = upower.Client():get_devices()

The same happens with playerctl:

local lgi = require("lgi")
local Playerctl = lgi.Playerctl
local player = Playerctl.Player{}

print(player:get_title())

I think I have all the needed introspection objects needed. Placing such code inside a GLib main loop doesn't change the output at all. Any ideas on what might be happening?

Start by reproducing the two minimal examples for UPowerGlib and Playerctl under both Lua and LuaJIT, then inspect the corresponding lgi introspection bindings. Compare the behavior with and without a GLib main loop and use the available crash output to narrow the cause. Done means identifying the source of the segmentation fault and confirming that both examples no longer crash.