b4 send --resend broken by 8cae1088cf605a12ed3207e7743fadcfa95c252a

[Dave Marquardt <davemarq@linux.ibm.com>]

commit 8cae1088cf605a12ed3207e7743fadcfa95c252a
Author: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Date:   Mon Jun 9 17:09:43 2025 -0400

    Further mypy typing enhancements
    
    Continued work to get ourselves to mypy strict clean runs. This mostly
    focuses on ez.py, but also tweaks a few other files where typing info
    was incorrect.
    
    Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

seems to have broken "b4 send --resend", which fails with

    CRITICAL: This is not a prep-managed branch or it was created by someone else.

The commit added a check for tag_msg after the else handling resend in cmd_send():

@@ -1802,12 +1873,16 @@ def cmd_send(cmdargs: argparse.Namespace) -> None:
 
         logger.info('Converted the branch to %s messages', len(patches))
 
+    if tag_msg is None:
+        logger.critical('CRITICAL: unable to get tag_msg from %s', mybranch)
+        sys.exit(1)
+

tag_msg isn't set in the resend path, so resend now fails.

-Dave