What does this implement/fix?

This is a bug-fix patch release. Changelog below:

2024-04-15 (3.45.3)

1. Fix a long-standing bug (going back to version 3.24.0) that might (rarely) cause the "old.*" values of an UPDATE trigger to be incorrect if that trigger fires in response to an UPSERT. Forum post 284955a3cd454a15.
2. Fix a bug in sum() that could cause it to return NULL when it should return Infinity. Forum post 23b8688ef4.
3. Other trifling corrections and compiler warning fixes that have come up since the previous patch release. See the timeline for details.

Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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