Many "empty" icons appear, when using this Applet, but not when using the default one

[JoeJoeTV]

If I activate this applet, a lot of "empty" icon(look like spacer applets) appear, that I can't get rid of.

Linux Mint 19.3 64 bit Cinnamon

[Majubs]

Same thing here, but it only happens when I close a program that had an icon in the system tray (Slack, for example), a small empty space appears. It goes back to normal after restarting Cinnamon.

I'm using Mint 19.1 with Cinnamon 4.0.10