exam: fix infinite recursion when no file extension

diff --git a/teleforma/exam/models.py b/teleforma/exam/models.py
index d9d8a7b043a57eb909c1b0ea4493d4d9dc314012..9c33c3cb2c5a4a66a8d09d315f46e76aa19ebdef 100755 (executable)
--- a/teleforma/exam/models.py
+++ b/teleforma/exam/models.py
@@ -517,8 +517,10 @@ def set_file_properties(sender, instance, **kwargs):
     if instance.file:
         trig_save = False
         if not instance.mime_type:
-            instance.mime_type = mimetype_file(instance.file.path)
-            trig_save = True
+            mime_type = mimetype_file(instance.file.path)
+            if mime_type:
+                instance.mime_type = mimetype_file(instance.file.path)
+                trig_save = True
         if not instance.sha1:
             instance.sha1 = sha1sum_file(instance.file.path)
             trig_save = True