TypeError: meta is null

[varac]

gnome-shell-timer doesn't start on my system

• PopOS 20.10 (based on Ubuntu 20.10)
• Gnome 3.38.3
• gnome-shell-timer 0.3.20+20171025-4

Feb 09 10:56:09 sancho.varac.net gnome-shell[3264]: JS ERROR: Extension timer@olebowle.gmx.com: TypeError: meta is null
                                                    _patchContainerClass/containerClass.prototype.child_set@resource:///org/gnome/shell/ui/environment.js:43:13
                                                    _patchContainerClass/containerClass.prototype.add@resource:///org/gnome/shell/ui/environment.js:52:18
                                                    _init@/usr/share/gnome-shell/extensions/timer@olebowle.gmx.com/extension.js:103:19
                                                    wrapper@resource:///org/gnome/gjs/modules/script/_legacy.js:82:27
                                                    enable@/usr/share/gnome-shell/extensions/timer@olebowle.gmx.com/extension.js:418:17
                                                    _callExtensionEnable@resource:///org/gnome/shell/ui/extensionSystem.js:168:32
                                                    _onEnabledExtensionsChanged/<@resource:///org/gnome/shell/ui/extensionSystem.js:496:35
                                                    _onEnabledExtensionsChanged@resource:///org/gnome/shell/ui/extensionSystem.js:496:14