fix light related crashes

drivers/gles2/rasterizer_scene_gles2.cpp

@@ -1169,7 +1169,7 @@ void RasterizerSceneGLES2::_add_geometry_with_material(RasterizerStorageGLES2::G
 
 				LightInstance *li = light_instance_owner.getornull(e->instance->light_instances[i]);
 
-				if (li->light_index >= render_light_instance_count || render_light_instances[li->light_index] != li) {
+				if (!li || li->light_index >= render_light_instance_count || render_light_instances[li->light_index] != li) {
 					continue; // too many or light_index did not correspond to the light instances to be rendered
 				}
 

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -1887,8 +1887,8 @@ void RasterizerSceneGLES3::_setup_light(RenderList::Element *e, const Transform
 		const RID *lights = e->instance->light_instances.ptr();
 
 		for (int i = 0; i < lc; i++) {
-			LightInstance *li = light_instance_owner.getptr(lights[i]);
-			if (li->last_pass != render_pass) //not visible
+			LightInstance *li = light_instance_owner.getornull(lights[i]);
+			if (!li || li->last_pass != render_pass) //not visible
 				continue;
 
 			if (li && li->light_ptr->type == VS::LIGHT_OMNI) {