Description of problem:
1. Login to Openbox.
2. Attempt to show a menu

Version-Release number of selected component:
openbox-3.6.1-10.fc29

Additional info:
reporter:       libreport-2.9.6
cmdline:        /usr/bin/python3 /usr/libexec/openbox-xdg-menu applications
crash_function: sort
exception_type: AttributeError
executable:     /usr/libexec/openbox-xdg-menu
interpreter:    python3-3.7.1-1.fc29.x86_64
kernel:         4.18.16-300.fc29.x86_64
runlevel:       N 5
type:           Python3
uid:            1000

Truncated backtrace:
Menu.py:301:sort:AttributeError: 'DesktopEntry' object has no attribute 'OnlyShowIn'

Traceback (most recent call last):
  File "/usr/libexec/openbox-xdg-menu", line 103, in <module>
    menu = xdg.Menu.parse(menufile)
  File "/usr/lib/python3.7/site-packages/xdg/Menu.py", line 1128, in parse
    return XMLMenuBuilder(debug).parse(filename)
  File "/usr/lib/python3.7/site-packages/xdg/Menu.py", line 644, in parse
    menu.sort()
  File "/usr/lib/python3.7/site-packages/xdg/Menu.py", line 232, in sort
    submenu.sort()
  File "/usr/lib/python3.7/site-packages/xdg/Menu.py", line 301, in sort
    if (entry.DesktopEntry.OnlyShowIn != [] and (
AttributeError: 'DesktopEntry' object has no attribute 'OnlyShowIn'

Local variables in innermost frame:
self: <xdg.Menu.Menu object at 0x7f812f2b9470>
_submenus: set()
_entries: set()
order: ['Merge', 'files']
menuentry: xfburn.desktop
entry: xfce4-about.desktop