Issue #22423: Unhandled exception in thread no longer causes unhandled

AttributeError when sys.stderr is None.

diff --cc Lib/threading.py
Simple merge

diff --cc Misc/NEWS
index 0c6c12d6e152f2a5695175569f2554291d783cb7,956721a756ad1b6eb50ae00b57406fd686065866..1c4a4b0b0683b19a057c5244b7af539266203521
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -137,8 -32,13 +137,11 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #22423: Unhandled exception in thread no longer causes unhandled
+   AttributeError when sys.stderr is None.
+ 
  - Issue #21091: Fix API bug: email.message.EmailMessage.is_attachment is now
 -  a method.  Since EmailMessage is provisional, we can change the API in a
 -  maintenance release, but we use a trick to remain backward compatible with
 -  3.4.0/1.
 +  a method.
  
  - Issue #21079: Fix email.message.EmailMessage.is_attachment to return the
    correct result when the header has parameters as well as a value.