Crash in garbage collector

When running a script without closing connection and cursor python sometimes crashes when closing these objects via garbage collector (Only reproducable on Windows).

Instead of if tp_dealloc method, objects should be cleared in tp_finalize.

import mariadb

c=mariadb.connect(user="root", db="test")

cursor=c.cursor()

cursor.execute("select * from t1")

$ python test.py

Windows fatal exception: access violation

Current thread 0x00004c88 (most recent call first):

  <no Python frame>