Fix for instructlab#254

Signed-off-by: ashna000 <[email protected]>

src/instructlab/training/multipack_sampler.py

@@ -76,7 +76,7 @@ def get_effective_samples_per_minibatch(num_tokens_per_gpu):
             padding=True,
         )
         batches = sampler.generate_batches()
-        return len(dataset) / len(batches)
+        return len(dataset) / len(batches if len(batches) > 0 else None
 
     samples_per_gpu = samples_per_minibatch / num_gpus