Fix error-handling when when "None"-type for ID is given in database

[SvenRoederer]

@MicDiFebo made it to add the following record into the database:

+----------+-------------------+---------------------+
| id       | name              | timestamp           |
+----------+-------------------+---------------------+
| None     | Mic               | 2019-08-21 17:26:25 |

this caused a fatal excetion on startup of registry:

pi@b33rnary-c0unter:/home/b33rnary-c0unt3r/b33rn4rycounter $ ./B33rn4ryRegistry.py
Traceback (most recent call last):
File "./B33rn4ryRegistry.py", line 200, in
window.refreshUserTable()
File "./B33rn4ryRegistry.py", line 68, in refreshUserTable
pID = str(int(row[0][2:], 16))
ValueError: invalid literal for int() with base 16: 'ne'