Paging Index Error when navigate from last page to previous page in Asp: GridView

Hi there,
I have a problem when I navigate my gridview from the last page to the previous page. It displays the following errors :
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Paging Index Error. Index: 2System.ArgumentOutOfRangeException: Index was out of range.
Must be non-negative and less than the size of the collection. Parameter name: index at System.Collections.ArrayList.get_Item(Int32 index) at System.Web.UI.WebControls.GridViewRowCollection.get_Item(Int32 index) at CASSET_WebApp.HomeForm.gvAssessment_RowCommand(Object sender,
GridViewCommandEventArgs e) in WebForm.aspx.cs:line 1942
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line 1942 is: GridViewRow row = this.gvAssessments.Rows[rowIndex];
I don't have any problem with other grids except this gridview has rowcommand in it.
I also attached my C# code for the Gridview_Rowcommand and asp code as well, see below. Please help I really appreciate

C# Code:
protected ...