Gracefully handle missing scale tensors (BF16 weights with stale index entries)

fp8_to_nvfp4_streaming.py

@@ -358,12 +358,16 @@ class ShardCache:
 
 
 def load_weight_and_scale(cache: ShardCache, weight_map, name):
-    """Load an FP8 weight with its weight_scale_inv companion (if any)."""
+    """Load an FP8 weight with its scale companion (if any)."""
     weight = cache.get(weight_map[name]).get_tensor(name)
     scale_name = name.replace(".weight", ".scale")
     scale = None
     if scale_name in weight_map:
-        scale = cache.get(weight_map[scale_name]).get_tensor(scale_name)
+        try:
+            scale = cache.get(weight_map[scale_name]).get_tensor(scale_name)
+        except Exception:
+            # Scale listed in index but not in shard (BF16 weights have no scale)
+            pass
     return weight, scale