New builds are triggered automatically without a commit after build cleanup strategy has cleaned all historical builds. For example:
ConfigurationA is containing build versions 1 (created a two weeks ago), 2 (created a week ago)

If there are no new commits done and your Build Cleanup Strategy is stating Reserve builds by days Reserve Days 4. Then after this 4 days are passed both build versions (1 and 2) are removed correctly, but QuickBuild will also decide to create a new version (which is identical to version 2) despite the fact there are no new commits done based on the fact it can't calculate if there is anything to be done as there is no previous build to evaluate against.

This is rather odd and I would expect that we will always keep reference on what the last commit was which was build rather then just for safety recreate it, because there was no previous build present.