initdb: Improve error recovery.

Hello there,

I would like to improve error recovery of initdb when the
password file is empty. The present code declares "Error 0"
as the cause of failure. It suffices to use ferrer() since
fgets() returns NULL also at a premature EOF.

In addition, a minor case is the need of a line feed in
order to print the error message on a line of its own
seems desirable.

Best regards, Mats Erik Andersson