[GnoVM] Missing method DecRefCount when deleting element in pointer slice

[leohhhn]

Description

GnoVM errors with Data: interface conversion: gnolang.RefValue is not gnolang.Object: missing method DecRefCount when trying to remove an element from a slice of pointers to structs. Check out the txtar below to reproduce.

Below test fails at calling DelEvent:

loadpkg gno.land/r/demo/evt $WORK

# start a new node
gnoland start

gnokey maketx call -pkgpath gno.land/r/demo/evt -func AddEvent -args "MyEvent1" -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
gnokey maketx call -pkgpath gno.land/r/demo/evt -func AddEvent -args "MyEvent2" -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1

gnokey maketx call -pkgpath gno.land/r/demo/evt -func DelEvent -args "MyEvent1" -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1

-- evt.gno --
package evt

type Event struct {
    name        string
}

type eventSlice []*Event

var events eventSlice

func init() {
	events = make(eventSlice, 0)
}

func AddEvent(name string) {
	events = append(events, &Event{name: name})
}

func DelEvent(name string) {
	for i, event := range events {
		if event.name == name {
			events = append(events[:i], events[i+1:]...)
			return
		}
	}
}

Found while working on #2372