While attempting to upgrade the documentation project to 4.5.1, I stumbled upon this problem:

1. The condition's message telling me that I need to have a property for the activation author key is unclear. It needs to be rewritten such that user can understand what it means, and what to do.
2. There are two different messages (see screenshot) - the first one comes from the condition's call to installContext.error, which is perhaps not necessary.
3. A FreeMarker exception shows in the logs, possibly because the ftl for the install screens try to get the error's exception message (which doesn't exist in this case)
   • Make those templates safer
   • Add an exception message in this case, if needed (but I suspect none of this is relevant), the condition returning false should be enough.