Fix pickling of 'reward_cfg["reward_scales"]' in hover example (Genesis-Embodied-AI#1340)

Author: ZaberKo

examples/drone/hover_env.py

@@ -1,5 +1,6 @@
 import torch
 import math
+import copy
 import genesis as gs
 from genesis.utils.geom import quat_to_xyz, transform_by_quat, inv_quat, transform_quat_by_quat
 
@@ -28,7 +29,7 @@ def __init__(self, num_envs, env_cfg, obs_cfg, reward_cfg, command_cfg, show_vie
         self.command_cfg = command_cfg
 
         self.obs_scales = obs_cfg["obs_scales"]
-        self.reward_scales = reward_cfg["reward_scales"]
+        self.reward_scales = copy.deepcopy(reward_cfg["reward_scales"])
 
         # create scene
         self.scene = gs.Scene(