Undefined properties and variables in JavaScript code

[Edenhofer]

Some variables are not properly declared in JavaScript and GNOME therefore logs some undesirable warnings.
Excerpt from journalctl:

DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/extension.js 376]: reference to undefined property Shell.ActionMode.MESSAGE_TRAY
DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/wikipedia_result_view.js 146]: reference to undefined property this._wikipedia_page.url
DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/wikipedia_page.js 233]: reference to undefined property pageprops.page_image
DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/wikipedia_page.js 126]: reference to undefined property page_data.images
DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/extension.js 311]: assignment to undeclared variable x
DATE MachineName gnome-shell[6715]: JS WARNING: [/home/username/.local/share/gnome-shell/extensions/[email protected]/extension.js 311]: assignment to undeclared variable y

I am using gnome-shell version 3.24.2, Linux version 4.11.5 and X as window system. The extension version is the one which is currently available at http://extensions.gnome.org.