Password dialog is not showed when using multiple screens. I can't enter password to unlock screen.

Reproducible: Always

Steps to Reproduce:
1. Have setup with two monitors. My setup is laptor screen + monitor _above_. See xrandr output below.
2. Lock screen.
3. Try to unlock.
Actual Results:  
Can't show password dialog.
I can enter password blindly after lock. But when I select "Unlock" from "Tool Box" menu or I hit Escape one or more times, I can't enter password even blindly.


$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 2100, maximum 16384 x 16384
VGA-0 disconnected (normal left inverted right x axis y axis)
LVDS-0 connected primary 1600x900+160+1200 (normal left inverted right x axis y axis) 345mm x 194mm
   1600x900       60.0*+   50.0  
DP-0 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1080      60.0 +   59.9     60.1     60.0     50.0  
   1920x1200      60.0* 
   1680x1050      60.0  
   1600x1200      60.0  
   1440x900       59.9  
   1280x1024      75.0     60.0  
   1280x720       60.0     59.9     50.0  
   1152x864       75.0  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     72.2     60.3  
   720x576        50.0     50.1  
   720x480        59.9     60.1  
   640x480        75.0     72.8     59.9     59.9  
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 disconnected (normal left inverted right x axis y axis)