Fix small bug/typo in misc.CreateNifti

Author: alexsavio

nipype/algorithms/misc.py

@@ -245,7 +245,7 @@ def _run_interface(self, runtime):
         else:
             affine = None
 
-        with open(self.inputs.header_file, 'rb') as data_file:
+        with open(self.inputs.data_file, 'rb') as data_file:
             data = hdr.data_from_fileobj(data_file)
 
         img = nb.Nifti1Image(data, affine, hdr)