Fix ec2_win_password to allow blank key_passphrase (#28791)

(cherry picked from commit 74f950936a)

lib/ansible/modules/cloud/amazon/ec2_win_password.py

@@ -133,6 +133,9 @@ def main():
 
     instance_id = module.params.get('instance_id')
     key_file = module.params.get('key_file')
+    if module.params.get('key_passphrase') is None:
+        b_key_passphrase = None
+    else:
         b_key_passphrase = to_bytes(module.params.get('key_passphrase'), errors='surrogate_or_strict')
     wait = module.params.get('wait')
     wait_timeout = int(module.params.get('wait_timeout'))