form: Check file pointer before dereferencing
form: Check file pointer before dereferencing

[It's not documented as being allowed to be NULL, but later in the
function there's a check, and GLib convention is generally that all
'out' parameters are allowed to be NULL whether it makes sense or not. -smcv]

Reviewed-by: Simon McVittie <2b470b34502dbf3ba4bcc04ea7e64f4e0e104f33@collabora.co.uk>
Reviewed-by: Dan Winship <a4113c7b8a2a3e6b96e702b23e93a123ab762619@gnome.org>
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=669479
Bug-NB: NB#297634

Distrotech/libsoup,fanc999/libsoup,Distrotech/libsoup,fanc999/libsoup,jwendell/libsoup,jwendell/libsoup,jwendell/libsoup,Distrotech/libsoup,jwendell/libsoup,fanc999/libsoup,fanc999/libsoup,Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,fanc999/libsoup