use sampler.toString() in BeanShell PreProcessor , HTTP JMeterProperty can not be replaced anymore

**xiangjian** ([Bug 58108](https://bz.apache.org/bugzilla//show_bug.cgi?id=58108&redirect=false)):
in BeanShell PreProcessor :

sampler.toString();
vars.put("sign","123");

${sign} can not be replaced by 123 in HttpSampler

please see Attachements

Created attachment [1.png](https://apache.github.io/jmeter-bugzilla-attachments/08/58108/32884/1.png): three pictures in one

Severity: normal
OS: All