HOTFIX: Migrated revocation

* adds handling for error raising if migrated revocation document missing, due to no existing document at all

konova/models/document.py

@@ -87,7 +87,7 @@ class AbstractDocument(BaseResource):
         """
         try:
             os.remove(self.file.file.name)
-        except FileNotFoundError:
+        except (FileNotFoundError, ValueError):
             # File seems to missing anyway - continue!
             pass
         super().delete(using=using, keep_parents=keep_parents)
@@ -113,7 +113,7 @@ class AbstractDocument(BaseResource):
         """
         try:
             os.remove(self.file.file.name)
-        except FileNotFoundError:
+        except (FileNotFoundError, ValueError):
             pass
         self.file = new_file
-        self.save()
+        self.save()