passwd: initialize pointers correctly

passwd: initialize pointers correctly

Fix for running passwd as root (or sudo passwd $USER).
Crashed on call to free(orig) during cleanup.

Fix regression from commit 17058a06c4333fc0c492c168c8a971ebd0fd5a5a
Root user never changes the orig pointer, so when cleaning up, passwd tried to
free orig=(char*)""
Example: sudo passwd $USER
Changing password for xxx
New password:
Bad password: too short
Retype password:
Passwords don't match
free(): invalid pointer
Aborted

function                                             old     new   delta
passwd_main                                          958     961      +3

Signed-off-by: Einar Jón <tolvupostur@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>