ReferenceError: weakly-referenced object no longer exists

[MrBitPythoner]

Hi there. I have been working on a library managment system. I am using MySQL as DB and Tkinter as GUI.

This error:

Error:
File "C:\Program Files\Python38\lib\site-packages\mysql\connector\cursor_cext.py", line 232, in executeif not self._cnx:ReferenceError: weakly-referenced object no longer exists

is being returned by this chunk of code:

def submit():
    search_words = search_entr.get()
    search_type = variable.get()
    if search_type == "Pick A Search Type":
        messagebox.showerror("Invalid Choice", "'Pick A Search Type' is not a valid search type.")
    else:
        global results
        if search_type == "ISBN":
            cur.execute("SELECT * FROM Books WHERE ISBN = %s", (search_words))
            results = cur.fetchball()
        if search_type == 'Title':
            cur.execute("SELECT * FROM Books where ITLE = %s", (search_words))
            results = cur.fetchball()
        if search_type == "Author":
            cur.execute("SELECT * FROM Books WHERE AUTHOR = %s", (search_words))
            results = cur.fetchball()

I have looked high and low for a solution, but have found none.

Please help

Thanks in advance