Do not fail when tag versions cannot be parsed.

[mauritsvanrees]

This can happen in lasttaglog, lasttagdiff, and bumpversion, with setuptools 66 or higher. Fixes issue #408.

I see a few test failures locally that should be unrelated. The tests expect a master branch, but there is a main branch. This probably differs per git version or local configuration. Let's see what gh-actions says.

[mauritsvanrees]

Okay, tests passed on gh-actions, so may be something local.
Still, I have added a commit to call git init -b main when setting up the example package in the tests. Now tests work fine locally again.

Well, there are a few test failures because I have this in my .pypirc:

[zest.releaser]
extra-message =
    [ci skip]

But never mind that for now.