Make OnQueryChange obey emptySearch

[davidmcatee-azure]

My use case: I am using withEmptySearch True to trigger the search on focus. If I type a letter, the OnQuery command happens as expected. But then if I press the backspace key to remove that character so that the input is empty again, I expect the OnQuery command to fire with the empty string. However, it does not fire at all. This change makes it so the OnQuery command does fire with the empty string only if emptySearch is True.

[sporto]

Thanks. Published 6.2.1