Make sure the list has been cleared before the values are read, otherwise libpurple will think the original selection was still active, causing changes not to apply.
Fixes #15629
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">