fix type inconsistency

[JLHwung]

This commit fixed type consistency between value of checkbox and the data `row-id' of the row.

If the identifier is { id: "12"} , checkbox value will be the exact string "12" while the data `row-id' ( converted from the type) will be integer 12. When rowSelect is true and user performs rowSelect, the selectedrows will be [12], however, if he/she uses selectbox, the selectedrows will be ["12"]. This type consistency will mess up all logic of deciding selected rows.

How can one trigger this bug?

set rowSelect and multiSelect be true.
and let data be [{id: "1"}, {id: "2"}].

rowSelect row 1 then unselect using checkbox, then rowSelect row 2 and one can see both row 1 and row 2 are selected.

[rstaib]

Thank you for the hint. I fixed the bug shortly. Actually, the bug wasn't here but there. Anyway your analysis work and the resulting information were very helpful. Maybe your next commit goes into the main repository ;-)