fuse.py, vidjilparser.py fix issue when no clones

allows vidjil files to contain no clones

tools/fuse.py

@@ -735,7 +735,8 @@ def main():
         if args.ijson:
             json_clones = vparser.extract(path_name)
             clones = json.loads(json_clones)
-            f += [c['id'] for c in clones["clones"]]
+            if clones["clones"] is not None:
+                f += [c['id'] for c in clones["clones"]]
         else:
             jlist = ListWindows()
             jlist.load(path_name, args.pipeline)

tools/vidjilparser.py

@@ -49,7 +49,10 @@ class VidjilWriter(object):
         else:
             if event == 'boolean':
                 value = str(value).lower()
-            mstr = '{}'
+            if value is None:
+                mstr = 'null'
+            else:
+                mstr = '{}'
         padding = ''
         if isinstance(value, string_types) :
             value = value.replace("\n", "\\n")