This is not an answer to bug report but rather a comment and alternate suggestion:
Since I do not need a screen saver (graphics) but do want a screen locker I did the following for my Fedora 27 install.
Remove xscreensaver then set power settings in xfce tool:
# dnf autoremove xscreensaver
xfce4-power-manager-settings
Add simple screen locker & check settings:
# dnf install slock (read man page to finish config)
Applications > Settings > Session & Startup > Advanced tab:
Y = Lock screen before sleep
Applications > Settings > Power Manager > System tab:
Y = Lock screen when system is going to sleep
+++
Press Ctrl+Alt+l which is mapped to the xflock4 script which looks for and runs slock.
After using slock to lock the screen, type your password the [Enter] to unlock.
There is no password dialogue box. While typing your password the screen will be blue.
If an incorrect password is typed the screen turn red ... so try again.