endless recursion when avp is not is found in the dictionary

[MuhammadTalhaRao]

In "/diam/dict/util.go" we try to find an avp and if we don't find it in its specific application and base dictionary the we get stuck in an endless loop. i fixed this issue for my library by adding a few checks but this issue need to fixed properly

if ok {
    return avp, nil
} else if appid != 0 {
    parentAppId, isScoppedApp := parentAppIds[appid]
    if isScoppedApp {
        // Try searching 'parent' dictionary
        appid = parentAppId
    } else {
        // Try searching the base dictionary.
        appid = 0
    }
    goto retry
} else {
          // here the endless recursion occurs

    if codeU32, isUint32 := code.(uint32); isUint32 {
        avp, err = p.FindAVP(origAppID, codeU32)
        if err != nil {
            return MakeUnknownAVP(origAppID, codeU32, vendorID), err
        }

        return avp, nil
    }
}