Fix bug in creating ThesisLink

Creating a new ThesisLink didn't save the `requested_by`
 field, causing trouble in for example the vet view
 for these specific objects.

theses/forms.py

@@ -42,6 +42,10 @@ class VetThesisLinkForm(RequestThesisLinkForm):
     justification = forms.CharField(widget=forms.Textarea(
         attrs={'rows': 5, 'cols': 40}), label='Justification (optional)', required=False)
 
+    def __init__(self, *args, **kwargs):
+        super(VetThesisLinkForm, self).__init__(*args, **kwargs)
+        self.order_fields(['action_option', 'refusal_reason', 'justification'])
+
     def vet_request(self, thesislink, user):
         if int(self.cleaned_data['action_option']) == VetThesisLinkForm.ACCEPT:
             thesislink.vetted = True

theses/views.py

@@ -38,6 +38,7 @@ class RequestThesisLink(CreateView):
     success_url = reverse_lazy('scipost:personal_page')
 
     def form_valid(self, form):
+        form.instance.requested_by = self.request.user.contributor
         messages.add_message(self.request, messages.SUCCESS,
                              strings.acknowledge_request_thesis_link)
         return super(RequestThesisLink, self).form_valid(form)