I haven't tested this, but if you want to try this fix you can open up the mod file and replace the section where it says "Spriteset_Map.prototype.disableFogOverlay" from line 28 to line 33 with this:
Spriteset_Map.prototype.disableFogOverlay = function() {
if (this.canDisableFogOverlay()) {
if (this.layerGraphics[1]) {
this.layerGraphics[1].visible = false;
}
if (this.layerGraphics[2]) {
this.layerGraphics[2].visible = false;
}
}
}