zero initialize remaining variables in LightsBuffer

src/tangerine.cpp

@@ -295,6 +295,8 @@ initLights(MemoryArena* arena, GLContext* gl_ctx, u32 max_lights)
 {
 	// FIXME: revisit for 'Scene' abstraction
 	LightsBuffer lights_buf;
+	lights_buf.active_p_lights = 0;
+	lights_buf.active_d_lights = 0;
 	lights_buf.max_p_lights = max_lights;
 	lights_buf.max_d_lights = max_lights;
 	lights_buf.p_lights = ARENA_ALLOC(arena, PointLight, max_lights);