Fix GradScaler resume bug - wrapped scaler.load_state_dict() in try/except at line 512. Allows resuming from checkpoints saved without AMP.

n.py

@@ -507,7 +507,11 @@ def load_ckpt(path, core, ar_h, sat_h, opt, scaler):
     ar_h.load_state_dict(ck["ar"])
     sat_h.load_state_dict(ck["sat"])
     opt.load_state_dict(ck["opt"])
-    scaler.load_state_dict(ck["scaler"])
+    try:
+        if ck.get("scaler"):
+            scaler.load_state_dict(ck["scaler"])
+    except RuntimeError:
+        print("[warn] Could not load scaler state, starting fresh")
     return ck.get("step", 0), ck.get("seen_tok", 0), ck.get("wall_time", time.time())
 
 def _safe_load_any(path: pathlib.Path, tgt: nn.Module, key: str | None = None):