Addendum:
From /var/log/lightdm/x-0-greeter.log:
*** Error in `/usr/sbin/lightdm-gtk-greeter': double free or corruption (fasttop): 0x00007f22865207c0 ***
Addendum:
From /var/log/ lightdm/ x-0-greeter. log:
*** Error in `/usr/sbin/ lightdm- gtk-greeter' : double free or corruption (fasttop): 0x00007f22865207c0 ***