fix openpilot speed regeression (#12039)

* set local_size=None if special.arg[0]=='i'

* add cast back

tinygrad/renderer/__init__.py

@@ -82,9 +82,9 @@ class ProgramSpec:
         if u.op is Ops.LOAD: self.ins.extend([x.arg for x in u.src[0].toposort() if x.op is Ops.DEFINE_GLOBAL])
         if u.op is Ops.SPECIAL:
           # NOTE: you have to set local_size and global_size to the base [1,1,1] outside this
+          if u.arg[0] == 'i': self.local_size = None
           special_size = self.local_size if u.arg[0] == 'l' else self.global_size
-          assert special_size is not None, f"special_size is None but found SPECIAL in uops {u}"
-          special_size[int(u.arg[-1])] = cast(int, u.src[0].ssimplify())  # TODO: the type here should be sint
+          if special_size is not None: special_size[int(u.arg[-1])] = cast(int, u.src[0].ssimplify())
       self.vars = sorted(self.vars, key=lambda v: v.arg)
       self.outs = sorted(dedup(self.outs))
       self.ins = sorted(dedup(self.ins))