fix: update iteration node to use correct variable segment types (#25315)

api/core/workflow/nodes/iteration/iteration_node.py

 from flask import Flask, current_app
 
 from configs import dify_config
-from core.variables import ArrayVariable, IntegerVariable, NoneVariable
+from core.variables import IntegerVariable, NoneSegment
 from core.variables.segments import ArrayAnySegment, ArraySegment
 from core.workflow.entities.node_entities import (
     NodeRunResult,
         if not variable:
             raise IteratorVariableNotFoundError(f"iterator variable {self._node_data.iterator_selector} not found")
 
-        if not isinstance(variable, ArrayVariable) and not isinstance(variable, NoneVariable):
+        if not isinstance(variable, ArraySegment) and not isinstance(variable, NoneSegment):
             raise InvalidIteratorValueError(f"invalid iterator value: {variable}, please provide a list.")
 
-        if isinstance(variable, NoneVariable) or len(variable.value) == 0:
+        if isinstance(variable, NoneSegment) or len(variable.value) == 0:
             # Try our best to preserve the type informat.
             if isinstance(variable, ArraySegment):
                 output = variable.model_copy(update={"value": []})