在工作流中直接引用应用int变量报错

**Describe the bug**

在工作流中直接引用带有默认值的integer应用变量，试运行报错如下：
错误："Workflow execution failure: invalid base 64"

Reproduce the issue in a workflow by directly referencing an application integer variable with a default value during a trial run. Start by tracing the source of the “invalid base 64” error in the workflow variable path. Done means the trial run accepts the integer variable and completes successfully.

Written by the indexing model from the issue text.