Fixes the file manager program (#21674)

The file manager did not properly go back to the file menu when it had
loaded a program, without reloading the whole window. It was caused by
it still having loaded the specific window, so the fix here is to simply
make sure it is no longer loaded.

code/modules/modular_computers/file_system/programs/system/file_browser.dm

@@ -19,8 +19,7 @@
 
 	var/obj/item/computer_hardware/hard_drive/HDD
 	var/obj/item/computer_hardware/hard_drive/portable/RHDD
-	if(error)
-		data["error"] = error
+	data["error"] = error
 	if(open_file)
 		var/datum/computer_file/data/file
 		var/datum/computer_file/script/script
@@ -44,6 +43,9 @@
 		if(!computer || !computer.hard_drive)
 			data["error"] = "I/O ERROR: Unable to access hard drive."
 		else
+			data["scriptdata"] = null
+			data["filedata"] = null
+			data["filename"] = null
 			HDD = computer.hard_drive
 			RHDD = computer.portable_drive
 			var/list/files = list()