If you find an error saying "gnome-control-center: error while loading shared libraries: libwebp.so.4: cannot open shared object file: No such file or directory" after upgrading Solus GNU/Linux 64 bit, you can follow this instruction to fix it:
sudo ln -s /usr/lib64/libwebp.so.6 /usr/lib64/libwebp.so.4
I personally found this error while upgrading (sudo eopkg upgrade) in Solus GNU/Linux version 1.2.1. The symptom was I could not launch GNOME Control Center, the GUI was not appearing. The source of problem was because GNOME Control Center asked for libwebp.so.4 but this file was gone and upgraded into libwebp.so.6 because of upgrading. So the solution was I just needed to create new "file" named libwebp.so.4 "linking" to the existing libwebp.so.6. The command above did this solution.