Clicking the search button when the search box is empty sometimes fails to show all titles

[Jaifroid]

I believe this is due to a protection feature in the search, which prevents lookup if the same string is entered twice in a row (instead, it should just display the previous search). However, there is no previous search if the field is blank and the user has just loaded a ZIM.

I believe the solution is to exempt comparison of current search and prefix if the search box is empty / blank / null, and/or checking that we have search results to display before invoking the protection.