Fixed error checking for valid user

wallamanta/walladb.py

@@ -13,7 +13,7 @@ def is_user_valid(telegram_user_id):
     con = sqlite3.connect(DB)
     cur = con.cursor()
     res = cur.execute(f"SELECT * FROM users WHERE telegram_user_id={telegram_user_id} AND active=True")
-    ret = res.fetchone() is None
+    ret = res.fetchone() != None
     con.close()
     return ret