Query parameters (ignore empty condition parameters)

Hey guys, I am new on wappler (from bubble.io).
I am trying to build a market place, but I am having some difficulties setting up a proper multi-parameters filter.
In fact, wappler seems not to ignore empty parameters. For example, when max price is empty, wappler count it as zero, subsequently does not display any item.
So how do I make it ignore entries without any user-defined parameters?

Additionally, how do we stop wappler from displaying the results in real-time?

It will be good to display results only the user hit “Enter/Return” or click the search button.