Fixed an error on closing envision when envision is connected. (#1843)

* Fixed an error on closing envision when envision is connected.

* Update changelog.

CHANGELOG.md

@@ -14,6 +14,7 @@ Copy and pasting the git commit messages is __NOT__ enough.
 ### Changed
 ### Deprecated
 ### Fixed
+- Fixed an exit error that occurs when envision attempts to close down.
 - Clarified the actions for `ActionSpaceType.Continuous` and `ActionSpaceType.ActuatorDynamic` in their respective docstrings.
 - Excluded from wheel any scenario build files in pattern `smarts/**/build/**/*.xml`.
 ### Removed

envision/client.py

@@ -173,7 +173,7 @@ def _write_log_state(
         with path.open("w", encoding="utf-8") as f:
             while True:
                 state = queue.get()
-                if type(state) is Client.QueueDone:
+                if isinstance(state, Client.QueueDone) or state is None:
                     break
 
                 if not isinstance(state, str):
@@ -260,7 +260,7 @@ def on_open(ws):
 
             while True:
                 state = state_queue.get()
-                if isinstance(type(state), Client.QueueDone):
+                if isinstance(state, Client.QueueDone) or state is None:
                     break
 
                 optionally_serialize_and_write(state, ws)