fix pop

Author: bpinsard

niworkflows/interfaces/bids.py

@@ -222,7 +222,7 @@ class BIDSDataGrabber(SimpleInterface):
 
     def __init__(self, *args, **kwargs):
         anat_only = kwargs.pop("anat_only")
-        anat_derivatives = kwargs.pop("anat_derivatives")
+        anat_derivatives = kwargs.pop("anat_derivatives", None)
         super(BIDSDataGrabber, self).__init__(*args, **kwargs)
         if anat_only is not None:
             self._require_funcs = not anat_only