Catch missing documents from the ocr queue list and display a message accordingly.

apps/ocr/models.py

@@ -1,5 +1,7 @@
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import ugettext
+from django.core.exceptions import ObjectDoesNotExist
 
 from documents.models import Document
 
@@ -51,4 +53,7 @@ class QueueDocument(models.Model):
         verbose_name_plural = _(u'queue documents')
 
     def __unicode__(self):
-        return unicode(self.document)
+        try:
+            return unicode(self.document)
+        except ObjectDoesNotExist:
+            return ugettext(u'Missing document.')

apps/ocr/views.py

@@ -35,7 +35,7 @@ def queue_document_list(request, queue_name='default'):
             'title':_(u'queued documents'),
             'hide_object':True,
             'extra_columns':[
-                {'name':'document', 'attribute': 'document'},
+                {'name':'document', 'attribute': lambda x: x.document if hasattr(x, 'document') else _(u'Missing document.')},
                 {'name':'submitted', 'attribute': lambda x: unicode(x.datetime_submitted).split('.')[0]},
                 {'name':'state', 'attribute': lambda x: x.get_state_display()},
                 {'name':'result', 'attribute':'result'},