[discuss] about genrating evt of packetloss

Hi, I see in packetloss, if sth is wrong in `GetSymsByStack()` , the evt won't be sent to the sink because we `continue` to skip the next steps :
```go
stacks, err := bpfutil.GetSymsByStack(uint32(event.StackId), p.objs.InspPlStack)
if err != nil {
log.Warnf("%s failed get sym by stack, err: %v", probeName, err)
continue
}
```

It means we finaly miss record this event. Actually in my production env, I do encounter this problem, I get some packetloss metric but no event.
So how about not `continue`,
```go
stacks, err := bpfutil.GetSymsByStack(uint32(event.StackId), p.objs.InspPlStack)
if err != nil {
log.Warnf("%s failed get sym by stack, err: %v", probeName, err)
// continue
evt.Message = "unknown"
} else {
var strs []string
for _, sym := range stacks {
if _, ok := ignoreSymbolList[sym.GetName()]; ok {
goto anotherLoop
}
strs = append(strs, sym.GetExpr())
}
evt.Message = strings.Join(strs, "\n")
}

Start at the packetloss handling around GetSymsByStack() and trace how the event reaches the sink. Verify the behavior when symbol lookup fails: packetloss events should still be emitted with the fallback message described in the issue, while successful lookups should retain their existing message.

Written by the indexing model from the issue text.