fix: datagrabber outfields

Author: satra

nipype/interfaces/io.py

@@ -439,6 +439,7 @@ def __init__(self, infields=None, outfields=None, **kwargs):
         undefined_traits = {}
         # used for mandatory inputs check
         self._infields = infields
+        self._outfields = outfields
         if infields:
             for key in infields:
                 self.inputs.add_trait(key, traits.Any)