The line in the [BT](https://github.com/geany/geany/blob/7d2e6182110a24b505c732f221dd79415f174024...) indicates that cbs.help is null, and thats set [here](https://github.com/geany/geany/blob/7d2e6182110a24b505c732f221dd79415f174024...) which as you can see will set NULL in some circumstances, maybe fast activation/deactivation gets it out of sync. Activation may include loading the .so and therefore may be a slow process (relatively speaking) so your fast click might intercept a previous action. Just check that the plugin is actually enabled, even though the help is enabled, maybe its getting out of sync.