Use a more friendly error message for empty sound names.

korman/nodes/node_messages.py

@@ -839,7 +839,10 @@ class PlasmaSoundMsgNode(idprops.IDPropObjectMixin, PlasmaMessageWithCallbacksNo
         # Remember that 3D stereo sounds are exported as two emitters...
         # But, if we only have one sound attached, who cares, we can just address the message to all
         msg = plSoundMsg()
-        sound_keys = tuple(soundemit.get_sound_keys(exporter, self.sound_name))
+        try:
+            sound_keys = tuple(soundemit.get_sound_keys(exporter, self.sound_name))
+        except ValueError as ex:
+            self.raise_error(f"Invalid sound specified {ex}")
         indices = frozenset((i[1] for i in sound_keys))
 
         if indices:

korman/properties/modifiers/sound.py

@@ -691,8 +691,10 @@ class PlasmaSoundEmitter(PlasmaModifierProperties):
             lfm_key.object.addStereizer(stereizer.key)
 
     def get_sound_keys(self, exporter, name=None, sound=None) -> Iterator[Tuple[plKey, int]]:
-        assert name or sound
+        assert name is not None or sound is not None
         if sound is None:
+            if not name:
+                raise ValueError(f"{self.id_data.name}: (No sound specified)")
             sound = next((i for i in self.sounds if i.name == name), None)
             if sound is None:
                 raise ValueError(f"{self.id_data.name}: Sound {name}")