systray-x: High CPU usage and laggy UI with version 0.9.6

Describe the bug With version 0.9.6 I see a high CPU usage and a laggy UI every time the content of a folder is modified (a new mail arrives, a mesage is moved/deleted etc.). This lasts several seconds. Downgrading to 0.9.5 solves the problem.

To Reproduce

1. install Systray-X 0.9.6
2. move amessage from one folder to another
3. check for CPU usage and UI responsiveness
4. check that after several seconds everything is back to normal

Expected behavior CPU usage and UI responsiveness should not show any troublesome behavior.

Desktop (please complete the following information):

• OS: ArchLinux
• Architecture: 64 bit
• Desktop type / Window Manager (KDE, Xfce, Cinnamon, MATE etc): Plasma
• Thunderbird version and arch (Tb xx.xx.x, 32 or 64 bit): 115.4.1
• Thunderbird package type (repository, mozilla binary, flatpak, snap, etc): ArchLinux [extra] repository
• Run echo $XDG_SESSION_TYPE in a terminal and report the results: x11
• Add-on version: 0.9.6
• App version
• Install type: github repository build, script installer, OBS repository: pacman package manager
• Used Qt library (default system repository, other OBS repo, self-compiled, Qt online installer): default system repository, version 5.15.11

Additional context Bug report on ArchLinux bug tracker