dmi_strip_metadata leads to removing alpha channel from the icon

[DTraitor]

dmi_strip_metadata leads to removing alpha channel from the icon
Here is the code I used:

/world
	fps = 25
	icon_size = 32
	view = 6

/mob/Login()
 	var/icon/test = icon('twitcher.dmi', "preview")
	fcopy(test, "temp.png")
	client << browse_rsc(icon("temp.png"), "first.png")
	call("rust_g", "dmi_strip_metadata")("temp.png")
	сlient << browse_rsc(icon("temp.png"), "second.png")

twitcher.dmi: https://cdn.discordapp.com/attachments/693217263934898190/1111983453760651324/twitcher.dmi

Code result:
first.png:

second.png:

[AnturK]

Yeah, not copying tRNS chunk from the original.

    if let Some(trns_chunk) = reader_info.trns.to_owned(){
        encoder.set_trns(trns_chunk);
    }

Simple fix, under palette copy.