Since pacman6 released, some users had an issue on add/remove software. Software opens and shutdowns itself. I found a solution for this problem. This is a short-term solution because of the complex structure of system.
Step 1. Download the neeeded file from http://dar.vin/libal
Step 2. Open terminal from where the file exists.
Step 3. Transfer file to /usr/lib folder with root permission (sudo cp file name /usr/lib) and reboot your system.
Step 4. Update your system from terminal (with sudo pacman -Syyu) and reboot again.
If you have some questions about problem, my answers may be late. I'm busy with my university lessons.