vala: Always bail if there are semantic errors
vala: Always bail if there are semantic errors

Previously introduced by 1430c461d4a45026331663989113feb195588255

GNOME/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,GNOME/vala