Moved from DEV-4248 (4)

Steps to reproduce:

1. Open Host -> Triggers -> Edit trigger
2. Add expression condition for function xmlxpath with all parameters filled
3. Click Expression constructor
4. Click to edit just added expression

Result:
XPath and Default parameters are empty

Expected:
All fields, that were filled, should be filled

Other cases: There are some functions where variables are filled, for example, trendstl, count. Affected functions are all String functions and Bitwise functions __ which use parameters