hotfix: only check current graph when excluding nodes in viz (tinygrad#8930)

Author: Qazalin

tinygrad/viz/serve.py

@@ -44,8 +44,9 @@ def uop_to_json(x:UOp) -> dict[int, tuple[str, list[int], str]]:
   for u in (toposort:=x.toposort):
     # always exclude DEVICE/CONST
     if u.op in {Ops.DEVICE, Ops.CONST}: excluded.add(u)
-    # only exclude CONST VIEW source if it has no other children
-    if u.op is Ops.CONST and len(u.src) != 0 and all((cr:=c()) is None or cr.op is Ops.CONST for c in u.src[0].children): excluded.update(u.src)
+    # only exclude CONST VIEW source if it has no other children in the graph
+    if u.op is Ops.CONST and len(u.src) != 0 and all(cr.op is Ops.CONST for c in u.src[0].children if (cr:=c()) is not None and cr in toposort):
+      excluded.update(u.src)
   for u in toposort:
     if u in excluded: continue
     argst = str(u.arg)