src/url_handlers.c: Don't use email_addr qvar directly in sign_up()

We set the email_addr variable to the email_addr query variable and use
that, however there was one place that was using the qvar directly.

Signed-off-by: Andrew Clayton <andrew@dnsandmx.com>
templates: sign_up: g_strstrip() the email address

There was an instance where someone had created an account but couldn't
log in. Turns out that they had managed to enter some whitespace at the
beginning of their email address. With browsers that support the 'email'
input type, the browser will catch this.

However, to cater for browsers that don't (and just for good practice
anyway) we should strip off any leading and trailing whitespace from the
email address.

Signed-off-by: Andrew Clayton <andrew@dnsandmx.com>