OpenCL FBP wrapper: fix extra_options check

nabu/reconstruction/fbp_opencl.py

@@ -57,7 +57,7 @@ class Backprojector:
             raise NotImplementedError()
         if padding_mode is not None:
             self._silx_fbp_extra_options["padding_mode"] = padding_mode
-        self._silx_fbp_extra_options["cutoff"] = extra_options.get("fbp_filter_cutoff", 1.)
+        self._silx_fbp_extra_options["cutoff"] = self.extra_options.get("fbp_filter_cutoff", 1.)
 
 
     def _get_scale_factor(self, scale_factor):