Fix FindSymbols

Author: enwask

devito/ir/iet/visitors.py

@@ -1088,7 +1088,7 @@ def visit_ThreadedProdder(self, o) -> Iterator[Any]:
     def visit_Operator(self, o) -> Iterator[Any]:
         yield from self._visit(o.body)
         yield from self.rule(o)
-        for i in o._dspace.parts:
+        for i in o._func_table.values():
             yield from self._visit(i)