[pgAdmin4][Patch]: Do not decrypt the password when the password is 'None'

Hi,

PFA patch to fix the issue where we were getting exception ValueError: IV must be 16 bytes long while decrypting the password.

RM#2765

Steps to re-produce:

1) Create new server using pgpass file, do not enter anything in password field.

2) Connect to server & open query tool (to make one or more connection with server)

3) Stop pgAdmin4 server from backend & start it again

4) Hard refresh the browser by removing the cache & cookies.

5) Expand the Server-Group in which you added that server, Check the console you will see the same error, this happens when we try to automatically restore the server connection while expanding the server nodes and that server connection do not have any password stored.