fix compiler uninitialized warning

src/game.cpp

@@ -111,7 +111,7 @@ selectOrbit(GameState* gs, GameOrbit* orbit)
 void
 changeOrbitColor(GameOrbit* orbit, vec3* color_data)
 {
-	GLBuffer* color_buf;
+	GLBuffer* color_buf = nullptr;
 	GLMesh* gl_mesh = &orbit->ellipse_entity->meshes[0];
 
 	for (u32 i = 0; i < gl_mesh->num_vertex_attrib_buffers; i ++) {