shadow element - parameter leak

Steps to Reproduce

run the attached example if-parameter-leak.zul

the example renders template contents dynamically based on the "vis" flag.
true -> render (default value if parameter omitted)
false -> don't render

Current Result

the rows for "value4" and "value6" are missing even though the "vis" parameter was not set.

Expected Result

all rows except "value3" (which uses vis="${false}") should render

Debug Information

the parameter vis-false of row-value3 is leaking into the subsequent omitted vis parameters.

the file if-parameter-leak-debug-info.zul renders additional information, showing that the same expression ${vis || vis eq null} inside the template sometimes evaluates correctly and sometimes fails using the leaked parameter value

Workaround

specify the "vis" parameter for every row, don't omit parameters.