Fix empty login on Chrome-based browsers

[fiammybe]

Fix #100
This will fix the long-standing bug that happens when you login from the user.php page (and not using the block on the homepage or somewhere else).

[MekDrop]

I think the bug is somewhere else. This fix could introduce another problem because it would always redirect when xoops_redirect is missing but some sections of code user.php doesn't needs such code so it will be not accessible.

Also, from GIT history I see that code line was changed for 1.3.8_beta but this bug become visible later.

[fiammybe]

Possibly. The reason we have a blank page is because, when you start from the user.php page to login, the redirect is empty, and in the end of the login process, ImpressCMS tries to redirect you to "", which won't work of course.

I'll try to find out why in this case the problem is there and why it is not present when I am using exactly the same code in the same file when trying to login using the user block on the frontpage.

[fiammybe]

In effect, you are correct. When I go to the /user.php page on a newly installed site, I have 2 ways of logging in : via the block in the side column, and via the block on the page itself.

The block in the side column works as expected, and this is the form data from the request that is generated:
uname: xxxx
pass: yyyy
xoops_redirect: /test14/user.php
op: login

When I try to login in the main block of the page, the form data is missing content for the xoops_redirect variable:
uname: xxxx
pass: yyyy
op: login
xoops_redirect:

Looking at the difference, in the block, the xoops_redirect parameter in the system_block_login.html template is using the $xoops_requesturi variable, where the user.php page is using the system_userform.html template with the $redirect_page variable.

When I put the $xoops_requesturi variable in the place of $redirect_page in the system_userform.html template, the login works as expected.

[fiammybe]

correct implementation is on #670