[pgAdmin][RM3269] Slider jumps up issue in DataView panel

Hi Hackers,
The attached patch fixes an issue where slider jumps up when new rows get
loaded while scrolling down in the DataView panel in the query tool.
Fix uses *rows_affected *field to create dummy rows (Apart from the
first *batch
of rows). *Dummy rows will be updated as and when they are required*. *As
total required rows are created initially, SlickGrid will not readjust its
height when the next batch of rows are loaded. Hence the jump up in the
slider will not happen.

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Thanks,
Nagesh