In Lubuntu 19.04, after opening the application menu from the panel, we need to press 2 times the "Up" key to go up in the menu

# Steps to reproduce

- Install a fresh Lubuntu 19.04,
- from the desktop, press the Super key (Windows key) to open the application menu,
- press the "Up" key to go up in the menu.

# Expected results

The cursor which is blinking in the search field should go up to "Lock Screen".

# Actual results

The cursor stay in the search field. We have to press the "Up" key a second time to make the cursor go up to "Lock Screen".

# Affected versions

Lubuntu 19.04
lxqt-panel 0.14.1
liblxqt 0.14.1
Qt 5.11.3

# Additional notes

Note 1: if instead of pressing the "Up" key we press the "Down" key, the cursor goes at the top of the menu, which is the normal behaviour.

Note 2: I can open the menu by clicking on it or by using the Super key, the behaviour is the same, I have to press the "Up" key twice to go up in the menu.

Note 3: if I use Shift+Tab after opening the menu instead of the "Up" key, I also have to press Shift+Tab twice to go up.

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: lxqt-panel 0.14.1-0ubuntu1
ProcVersionSignature: Ubuntu 5.0.0-13.14-generic 5.0.6
Uname: Linux 5.0.0-13-generic x86_64
ApportVersion: 2.20.10-0ubuntu27
Architecture: amd64
CurrentDesktop: LXQt
Date: Thu May 2 22:32:40 2019
InstallationDate: Installed on 2019-05-02 (0 days ago)
InstallationMedia: Lubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
SourcePackage: lxqt-panel
UpgradeStatus: No upgrade log present (probably fresh install)