Parsing of post fields when switching between 'form data' and 'raw data' doesn't work well.

Steps to reproduce:
1) create a web scenario with single step and put the same 16K character string in 'raw post' field. Make sure you have two parameters (let's say, a1 and a2).
2) switch to 'form data' mode and make sure there are both fields parsed one per line.
3) save scenario.
4) open it once again and navigate to step popup. Observe that as expected, there are 2 rows in 'post fields' tab.
5) switch to 'row data' and then back to 'form data' mode.

Result:
There are 3 or 4 fields instead of 2 fields as before.

Pair manager issues rendering new pairs

Steps to reproduce:
1) Click "Create new web scenario"
2) Navigate to "Steps" tab.
3) Click "Add"
4) Observe that info window shows one empty pair in "Post fields" section.
5) Now toggle "Post type" to "Raw mode", then back to "Form data".

Result
One empty pair in "Post fields" section has disappeared.