hash-library | Portable C++ hashing library | Hashing library

I tried creating a hash map storing its inputs as linked list nodes using separated chaining. The first display function gives a desirable output, but the next one resets the entire array to empty nullptr. I used the same class object so shouldn't it give the same result each time? Was it because of the destructor somehow? I thought it may be because I inserted a new item so I deleted it and the same thing still persists. My only suspect is the display() function but please point out if the problem comes from somewhere else.

Sorry if the post is so long, I want to make sure everyone can see the entire code to spot the problem.