fix straylight cpp NAN bug; fix fgs no straylight bug

ObservationSim/Instrument/Filter.py

@@ -116,7 +116,7 @@ class Filter(object):
             s_pix, spec = sl.calculateStrayLightGrating(grating = self.filter_type.upper())
             self.sky_background = s_pix
             self.zodical_spec = spec
-        else:
+        elif self.filter_type.lower() in ["nuv","u","g","r","i","z","y"]:
             s_pix = sl.calculateStrayLightFilter(filter=self.filter_type.lower())
             self.sky_background = s_pix
             self.zodical_spec = None