[MIRROR] Fix runtime with ntos apps and improves code involved in the runtime (#854)

* Fix runtime with NTOS apps and improve code involved (#53779)

There exists a specific state where ui.open() can be called yet the
result would be a null window and such behaviour would be intentional.
The following CRASH in ui.send_asset() would thus be misleading,
because send_asset() was called after open().

This PR adds more information to the CRASH about when the failure state
can occur, makes open() return a value based on whether it actually
opened a new pooled window or not, and makes sure modular computer apps
don't send_assets unless a new pooled window was created.

* Fix runtime with ntos apps and improves code involved in the runtime

Co-authored-by: Timberpoes <silent_insomnia_pp@hotmail.co.uk>

code/modules/modular_computers/computers/item/computer_ui.dm

@@ -37,8 +37,8 @@
 	if (!ui)
 		ui = new(user, src, "NtosMain")
 		ui.set_autoupdate(TRUE)
-		ui.open()
-		ui.send_asset(get_asset_datum(/datum/asset/simple/headers))
+		if(ui.open())
+			ui.send_asset(get_asset_datum(/datum/asset/simple/headers))
 
 
 /obj/item/modular_computer/ui_data(mob/user)

code/modules/modular_computers/file_system/program.dm

@@ -179,8 +179,8 @@
 	ui = SStgui.try_update_ui(user, src, ui)
 	if(!ui && tgui_id)
 		ui = new(user, src, tgui_id, filedesc)
-		ui.open()
-		ui.send_asset(get_asset_datum(/datum/asset/simple/headers))
+		if(ui.open())
+			ui.send_asset(get_asset_datum(/datum/asset/simple/headers))
 
 // CONVENTIONS, READ THIS WHEN CREATING NEW PROGRAM AND OVERRIDING THIS PROC:
 // Topic calls are automagically forwarded from NanoModule this program contains.