[code][model] Improve handling of empty description

This ensure that the corresponding file is created even if
empty.

beat/web/code/models.py

@@ -148,13 +148,15 @@ class CodeManager(StoredContributionManager):
             code_db.source_code = code
 
         # Check the provided description
-        if not(description):
+        if description is None:
             if previous_version is not None:
-                code_db.description = previous_version.description
+                description = previous_version.description
             elif fork_of is not None:
-                code_db.description = fork_of.description
-        else:
-            code_db.description = description
+                description = fork_of.description
+            else:
+                description = ''
+
+        code_db.description = description
 
         try:
             code_db.save()