Creating multiple times database leads to non-functional
Hi,
This command:
```
/usr/bin/pakon-maintain create-databases
```
does not give any output and I already had the database and it was working, but when I try to call it, then it leads to this error:
```
root@turris:~# pakon-show
Traceback (most recent call last):
File "/usr/bin/pakon-show", line 33, in <module>
sys.exit(load_entry_point('pakon==1.2.2', 'console_scripts', 'pakon-show')())
File "/usr/lib/python3.9/site-packages/pakon/show/__main__.py", line 116, in main
File "/usr/lib/python3.9/json/__init__.py", line 346, in loads
File "/usr/lib/python3.9/json/decoder.py", line 337, in decode
File "/usr/lib/python3.9/json/decoder.py", line 355, in raw_decode
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
```
The script should check, if the database is alright and don't create a new one.
issue