Keyboard shortcuts which contain `parenleft` or 'parenright' do not function

Shortcuts created via xfwm4-settings which contain the ( or ) characters, aka Shift+9 or Shift+10, do not function when the key sequence is entered.

To reproduce this issue, create a shortcut which contains one of these characters character, e.g. "Shift + Ctrl + (", attempt to use it, and observe the shortcut not working correctly when other similar shortcuts work fine, e.g. "Shift + Ctrl + *".

I discovered this issue because I use the shortcut "Shift + Alt + [number]" to move a window to a given workspace, and I am never able to move a window to workspaces 9 and 10 unless the key combination used to perform this action is adjusted to not include the bracket characters.

I have managed to reproduce this issue on two of my machines, one being a desktop and one being a laptop, and on both I am using xfwm4 as currently distributed in the official Gentoo ebuild repositories at version 4.18.0.