Use .itemsize to get dtype size for fp8.

comfy/model_management.py

@@ -430,6 +430,13 @@ def dtype_size(dtype):
     dtype_size = 4
     if dtype == torch.float16 or dtype == torch.bfloat16:
         dtype_size = 2
+    elif dtype == torch.float32:
+        dtype_size = 4
+    else:
+        try:
+            dtype_size = dtype.itemsize
+        except: #Old pytorch doesn't have .itemsize
+            pass
     return dtype_size
 
 def unet_offload_device():