fix: guard against deleted QGIS layers and empty fault traces

- to_dict() crashed with RuntimeError on save if a basal contacts,
  fault traces, or structural orientations layer had been deleted
  from the project while still referenced; now caught like the
  existing dem_layer guard, and dem_layer_name is initialised so a
  caught DEM error can't leave it undefined either.
- AllSampler returned a columnless DataFrame when a fault trace
  layer had no sampled points, causing a KeyError on 'feature_id'
  downstream in update_fault_points.

Author: lachlangrose

loopstructural/main/data_manager.py

@@ -1099,15 +1099,31 @@ def to_dict(self):
 
         # Replace layer objects with layer names
         if basal_contacts and 'layer' in basal_contacts and basal_contacts['layer'] is not None:
-            basal_contacts['layer'] = basal_contacts['layer'].name()
+            try:
+                basal_contacts['layer'] = basal_contacts['layer'].name()
+            except RuntimeError as e:
+                self.logger(message=f"Error getting basal contacts layer name: {e}", log_level=2)
+                basal_contacts['layer'] = None
         if fault_traces and 'layer' in fault_traces and fault_traces['layer'] is not None:
-            fault_traces['layer'] = fault_traces['layer'].name()
+            try:
+                fault_traces['layer'] = fault_traces['layer'].name()
+            except RuntimeError as e:
+                self.logger(message=f"Error getting fault traces layer name: {e}", log_level=2)
+                fault_traces['layer'] = None
         if (
             structural_orientations
             and 'layer' in structural_orientations
             and structural_orientations['layer'] is not None
         ):
-            structural_orientations['layer'] = structural_orientations['layer'].name()
+            try:
+                structural_orientations['layer'] = structural_orientations['layer'].name()
+            except RuntimeError as e:
+                self.logger(
+                    message=f"Error getting structural orientations layer name: {e}",
+                    log_level=2,
+                )
+                structural_orientations['layer'] = None
+        dem_layer_name = None
         if self.dem_layer is not None:
             try:
                 dem_layer_name = self.dem_layer.name()

loopstructural/main/model_manager.py

@@ -94,6 +94,8 @@ def __call__(self, line: gpd.GeoDataFrame, dem: Callable, use_z: bool) -> pd.Dat
                     {'X': coords[0], 'Y': coords[1], 'Z': z, 'feature_id': feature_id, **attributes}
                 )
             feature_id += 1
+        if not points:
+            return pd.DataFrame(points, columns=['X', 'Y', 'Z', 'feature_id'])
         df = pd.DataFrame(points)
         return df