Fix crash on ambient map update outside landscape bounds (#1216)

src/landscape/C4Landscape.cpp

@@ -3316,6 +3316,8 @@ void C4Landscape::PrepareChange(C4Rect BoundingBox)
 
 void C4Landscape::FinishChange(C4Rect BoundingBox)
 {
+	// Intersect bounding box with landscape
+	BoundingBox.Intersect(C4Rect(0, 0, Width, Height));
 	// update render
 	if(pLandscapeRender)
 		pLandscapeRender->Update(BoundingBox, this);

src/landscape/fow/C4FoWAmbient.cpp

@@ -126,6 +126,9 @@ void C4FoWAmbient::CreateFromLandscape(const C4Landscape& landscape, double reso
 
 void C4FoWAmbient::UpdateFromLandscape(const C4Landscape& landscape, const C4Rect& update)
 {
+	// Nothing to do?
+	if(update.Wdt == 0 || update.Hgt == 0) return;
+
 	assert(Tex != 0);
 
 	// Factor to go from zoomed to landscape coordinates