PS: I'm not sure, but I'm guessing that this line in the stack trace might possibly explain the problem:
Package com.joaomgcd.taskersettings has not requested permission android.permission.WRITE_SECURE_SETTINGS
Could it be that
android.permission.WRITE_SECURE_SETTINGS is not present in the Tasker app's manifest?
Again, I'm running the lastest Tasker beta.