lua reset_mixer script: ignore hidden io processors like "main out"

* fixes a problem in Mixbus where the reset script will kill audio output

share/scripts/reset_mixer.lua

@@ -152,7 +152,9 @@ function factory() return function()
 				if prefs["io"] then
 					local io_proc = proc:to_ioprocessor()
 					if not(io_proc:isnil()) then
-						queue[#queue + 1] = proc
+						if insert:is_channelstrip() or not(insert:display_to_user()) then
+							queue[#queue + 1] = proc
+						end
 					end
 				end
 			end