Fix CSGPolygon Buffer Overflow

Immediate meshes do not have geometry of type Surface so we check
to see the mesh isn't immediate before trying to cast to surface
to check for octahedral compression

drivers/gles2/rasterizer_scene_gles2.cpp

@@ -2429,7 +2429,7 @@ void RasterizerSceneGLES2::_render_render_list(RenderList::Element **p_elements,
 
 		state.scene_shader.set_conditional(SceneShaderGLES2::USE_PHYSICAL_LIGHT_ATTENUATION, storage->config.use_physical_light_attenuation);
 
-		bool octahedral_compression = ((RasterizerStorageGLES2::Surface *)e->geometry)->format & VisualServer::ArrayFormat::ARRAY_FLAG_USE_OCTAHEDRAL_COMPRESSION;
+		bool octahedral_compression = e->instance->base_type != VS::INSTANCE_IMMEDIATE && ((RasterizerStorageGLES2::Surface *)e->geometry)->format & VisualServer::ArrayFormat::ARRAY_FLAG_USE_OCTAHEDRAL_COMPRESSION;
 		if (octahedral_compression != prev_octahedral_compression) {
 			state.scene_shader.set_conditional(SceneShaderGLES2::ENABLE_OCTAHEDRAL_COMPRESSION, octahedral_compression);
 			rebind = true;

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -2114,7 +2114,7 @@ void RasterizerSceneGLES3::_render_list(RenderList::Element **p_elements, int p_
 
 		state.scene_shader.set_conditional(SceneShaderGLES3::USE_PHYSICAL_LIGHT_ATTENUATION, storage->config.use_physical_light_attenuation);
 
-		bool octahedral_compression = ((RasterizerStorageGLES3::Surface *)e->geometry)->format & VisualServer::ArrayFormat::ARRAY_FLAG_USE_OCTAHEDRAL_COMPRESSION;
+		bool octahedral_compression = e->instance->base_type != VS::INSTANCE_IMMEDIATE && ((RasterizerStorageGLES3::Surface *)e->geometry)->format & VisualServer::ArrayFormat::ARRAY_FLAG_USE_OCTAHEDRAL_COMPRESSION;
 		if (octahedral_compression != prev_octahedral_compression) {
 			state.scene_shader.set_conditional(SceneShaderGLES3::ENABLE_OCTAHEDRAL_COMPRESSION, octahedral_compression);
 			rebind = true;