Fix 'missing required key "timestamp" in block'

Created by: ollieparanoid

This happens, when a virtual package is still installed. We use the .pmbootstrap virtual package nowadays to install packages, that should not be explicitly marked as installed. Anyway, when an error happens before the .pmbootstrap package gets uninstalled (which happens directly after installing it), and you do anything with pmbootstrap, it will fail to parse the package database. Because virtual packages like .pmbootstrap don't have the "timestamp" key in that database file.

Workaround: pmbootstrap zap