fix list bugs

Author: Licini

src/compas_viewer/scene/buffermanager.py

@@ -115,7 +115,7 @@ def _add_buffer_data(self, obj: Any, buffer_type: str) -> None:
 
         # Convert to numpy arrays
         pos_array = np.array(positions, dtype=np.float32).flatten()
-        col_array = np.array([c.rgba for c in colors] if isinstance(colors[0], Color) else colors, dtype=np.float32).flatten()
+        col_array = np.array([c.rgba for c in colors] if len(colors) > 0 and isinstance(colors[0], Color) else colors, dtype=np.float32).flatten()
         elem_array = np.array(elements, dtype=np.int32).flatten()
 
         if buffer_type == "_frontfaces_data" or buffer_type == "_backfaces_data":

src/compas_viewer/scene/sceneobject.py

@@ -183,11 +183,11 @@ def _update_bounding_box(self, positions: Optional[list[Point]] = None):
         """Update the bounding box of the object"""
         if positions is None:
             positions = np.array([]).reshape(0, 3)
-            if self._points_data is not None:
+            if self._points_data is not None and len(self._points_data[0]) > 0:
                 positions = np.vstack([positions, self._points_data[0]])
-            if self._lines_data is not None:
+            if self._lines_data is not None and len(self._lines_data[0]) > 0:
                 positions = np.vstack([positions, self._lines_data[0]])
-            if self._frontfaces_data is not None:
+            if self._frontfaces_data is not None and len(self._frontfaces_data[0]) > 0:
                 positions = np.vstack([positions, self._frontfaces_data[0]])
             if len(positions) == 0:
                 return