Fix out of range exception when try to load a particle node with empty sizes array (bug #4804)

CHANGELOG.md

@@ -20,6 +20,7 @@
     Bug #4778: Interiors of Illusion puzzle in Sotha Sil Expanded mod is broken
     Bug #4800: Standing collisions are not updated immediately when an object is teleported without a cell change
     Bug #4803: Stray special characters before begin statement break script compilation
+    Bug #4804: Particle system with the "Has Sizes = false" causes an exception
     Feature #2229: Improve pathfinding AI
     Feature #3442: Default values for fallbacks from ini file
     Feature #3610: Option to invert X axis

components/nifosg/nifloader.cpp

@@ -822,7 +822,9 @@ namespace NifOsg
                 if (particle.vertex < int(particledata->colors.size()))
                     partcolor = particledata->colors.at(particle.vertex);
 
-                float size = particledata->sizes.at(particle.vertex) * partctrl->size;
+                float size = partctrl->size;
+                if (particle.vertex < int(particledata->sizes.size()))
+                    size *= particledata->sizes.at(particle.vertex);
 
                 created->setSizeRange(osgParticle::rangef(size, size));
                 box.expandBy(osg::BoundingSphere(position, size));