Fix unexpected 400

[sstrigler]

Fixes EMQX-7817

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/emqx/emqx/blob/master/CONTRIBUTING.md.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/ dir
• For EMQX 4.x: appup files updated (execute scripts/update-appup.sh emqx)
• For internal contributor: there is a jira ticket to track this change, and another jira tickt to track doc updates (if any)
• In case of non-backward compatible changes, reviewer should check this item as a write-off, and add details in Backward Compatibility section

Backward Compatibility

More information

[coveralls]

Pull Request Test Coverage Report for Build 3368531324

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 42 unchanged lines in 14 files lost coverage.
• Overall coverage decreased (-0.06%) to 77.979%

---

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_management/src/emqx_mgmt_api_trace.erl	1	80.41%
apps/emqx/src/emqx_config.erl	1	84.83%
apps/emqx/src/emqx_connection.erl	1	87.64%
apps/emqx/src/emqx_listeners.erl	1	85.12%
apps/emqx/src/emqx_router_helper.erl	1	86.27%
apps/emqx/src/emqx_broker.erl	2	82.42%
apps/emqx/src/emqx_channel.erl	2	87.48%
apps/emqx/src/emqx_cm.erl	2	88.99%
apps/emqx/src/persistent_session/emqx_persistent_session.erl	2	93.01%
apps/emqx_gateway/src/emqx_gateway_cm.erl	3	73.45%

Totals
Change from base Build 3361588080:	-0.06%
Covered Lines:	20864
Relevant Lines:	26756

---

💛 - Coveralls