The white void appears when heading north in two locations:

Mile Post 130.5 by South Raub between Linden to Lafayette 
Monon to Bloomington Division

Milepost 136.5 in Frankfort
Monon to Indianapolis Division

There are two fixes.

1) Do nothing to the simulator.
   When the void appears save the simulation (F2)
   Exit the simulation
   Load the simulation you just saved
   The similation is normal again and the void is gone.

2) Install two train sim patches on this web page.

Install trainupdate-patch 1.2 then Patch Patch 1.7.022420...............


Download:
trainupdate-patch 1.2
Install trainupdate-patch 1.2
Download:
Patch Patch 1.7.022420
Install Patch Patch 1.7.022420
In that order................