The calc_transmission may also have no coating information

Signed-off-by: Brianna Major <brianna.major@taloid.khq.kitware.com>

hexrd/instrument/hedm_instrument.py

@@ -2193,9 +2193,13 @@ def calc_transmission(self, rMat_s: np.ndarray = None) -> dict[str, np.ndarray]:
         energy = self.beam_energy
         transmissions = {}
         for det_name, det in self.detectors.items():
+            transmission = 1
             transmission_filter, transmission_phosphor = (
                 det.calc_filter_coating_transmission(energy))
-            transmission = transmission_filter * transmission_phosphor
+            if det.filter.thickness > 0:
+                transmission *= transmission_filter
+            if det.phosphor.thickness > 0:
+                transmission *= transmission_phosphor
             if self.physics_package is not None:
                 transmission_physics_package = (
                     det.calc_physics_package_transmission(