fixed crashing when no labels are present in the batch

luxonis_train/attached_modules/losses/adaptive_detection_loss.py

@@ -1,4 +1,4 @@
-from typing import Literal
+from typing import Literal, cast
 
 import torch
 import torch.nn.functional as F
@@ -209,8 +209,11 @@ def forward(
     def _preprocess_target(self, target: Tensor, batch_size: int, scale_tensor: Tensor):
         """Preprocess target in shape [batch_size, N, 5] where N is maximum number of
         instances in one image."""
-        sample_ids, counts = torch.unique(target[:, 0].int(), return_counts=True)
-        out_target = torch.zeros(batch_size, counts.max(), 5, device=target.device)
+        sample_ids, counts = cast(
+            tuple[Tensor, Tensor], torch.unique(target[:, 0].int(), return_counts=True)
+        )
+        c_max = int(counts.max()) if counts.numel() > 0 else 0
+        out_target = torch.zeros(batch_size, c_max, 5, device=target.device)
         out_target[:, :, 0] = -1
         for id, count in zip(sample_ids, counts):
             out_target[id, :count] = target[target[:, 0] == id][:, 1:]