Material design icons not showing on Google Calendar when extension is active on Firefox

[gezegond]

Here's how it looks with the firefox extension enabled:

Here's how it looks (correctly) with the firefox extension disabled:

Please note that it's always buggy when extension is enabled, regardless of extension settings. It will remain buggy if the Google Calendar option for the extension is disabled for instance.

[amirghm]

Have the same issue, it is also happened in Google Chrome too