Unexpected command object errors rendered

Trigger the following urls in the example:
/<app-name>/test/searchForm results in form being properly rendered without errors
/<app-name>/test/search results in form being rendered with errors though the command object passed via the model is not validated,
so I would expect an empty form being rendered just as in the first case

It seems that errors are always rendered if there is a command object parameter being declared in the closure independently of the actual object that is passed to the view. Complete code is given in attachment.

class TestController {

def searchForm =

{ render(view: 'search', model:['cmd': new SearchCommand()]) // properly renders form without error messages, expected behavior }

def search =

{SearchCommand c -> if(!params.search) return ['cmd': new SearchCommand()] // renders form with error messages, unexpected behavior ... }

}
class SearchCommand {
String zip
static constraints =

{ zip(nullable:false,blank:false,maxSize:5) }

}

Workaround: Separate method to render empty form.