Support instruments with no default physics package

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

hexrdgui/main_window.py

@@ -1636,6 +1636,15 @@ def action_apply_absorption_correction_toggled(self, b):
             HexrdConfig().apply_absorption_correction = b
             return
 
+        # Make sure the physics package exists first
+        if HexrdConfig().physics_package is None:
+            msg = (
+                'Physics package must be set before absorption correction can be '
+                'applied. See the "Physics Package" editor under the "Edit" menu.'
+            )
+            QMessageBox.warning(self.ui, 'HEXRD', msg)
+            return
+
         # Get the user to first select the absorption correction options
         d = AbsorptionCorrectionOptionsDialog(self.ui)
         if not d.exec():

hexrdgui/physics_package_manager_dialog.py

@@ -131,6 +131,9 @@ def setup_form(self):
 
         # Set default values
         physics = HexrdConfig().physics_package
+        if physics is None:
+            return
+
         # PINHOLE
         self.ui.pinhole_material.setCurrentText(physics.pinhole_material)
         self.ui.pinhole_density.setValue(physics.pinhole_density)
@@ -189,7 +192,9 @@ def material_changed(self, index, category):
             self.density_inputs[category].setValue(density)
         else:
             self.density_inputs[category].setValue(0.0)
-        self.ui.absorption_length.setValue(HexrdConfig().absorption_length())
+
+        if HexrdConfig().physics_package is not None:
+            self.ui.absorption_length.setValue(HexrdConfig().absorption_length())
 
     def accept_changes(self):
         materials = {}