Thanks for the notification of this behavior. We have been able to reproduce it locally and will include a fix in the next release. Just a quick side note, for the interim, if you manually select the entry from the assigned category, as opposed to searching for it, deleting the entry does properly work in that case.
I can confirm that the delete entry toolbar button item is disabled while displaying search results, this is a validation bug. However, the Delete command is available under the Edit menu while displaying search results, and is also accessible via the keyboard shortcut ⌘ delete, and it does appear to still be working correctly, deleting the selected entry result. Does that match what you are seeing?