network: Fix compile-time warning

Missing include.

https://bugzilla.gnome.org/show_bug.cgi?id=734472
network: Don't stop validating when we get an error

The previous code would stop validating when an error occurred which
meant that when a page contained multiple errors, only the first one(s)
to be checked would appear in red.

Now, all the errors will appear in red.

https://bugzilla.gnome.org/show_bug.cgi?id=734472