when an iframe is nested in a Modal window (or popup) and the window is detached the iframe reloads its content before being removed

Run the attached example:
click "open"
-> the content of iframeSimple is created (see server log message "*** CREATED ***")

click the button "remove (loads iframe again)"
-> the window is getting detached but the iframe reloads before getting removed from the dom (check network tab in browser) and server log ("*** CREATED ***")

the example also contains a workaround (second button),
avoiding the reload by clearing the iframe src attribute in a widget onClick listener
w:onClick="zk.Widget.$('$iframe').setSrc('');"
-> no reload occurs (expected)