fix: Make `sharp_linalg.rotation_matrices_from_quaternions` robust to empty tensor inputs.

model_utils.py

@@ -37,6 +37,17 @@ from sharp.cli.predict import DEFAULT_MODEL_URL, predict_image
 from sharp.models import PredictorParams, create_predictor
 from sharp.utils import io
 from sharp.utils.gaussians import save_ply
+from sharp.utils import linalg as sharp_linalg
+
+_orig = sharp_linalg.rotation_matrices_from_quaternions
+
+def _safe_rotation_matrices_from_quaternions(quaternions: torch.Tensor) -> torch.Tensor:
+    # Handles shape (..., 4)
+    if quaternions.numel() == 0:
+        return quaternions.new_empty((*quaternions.shape[:-1], 3, 3))
+    return _orig(quaternions.contiguous())
+
+sharp_linalg.rotation_matrices_from_quaternions = _safe_rotation_matrices_from_quaternions
 
 # -----------------------------------------------------------------------------
 # Helpers