listbox with auxhead (hflex vs span conflict)

Steps to Reproduce

auxhead-span-flex-conflict.zul

Current Result

Expected Result

both listboxes should look the same
when hflex is used on a column, span="true" is redundant and should be ignored

the behavior is still as expected in 9.5.0.3

Debug Information

Workaround

remove span="true" when using hflex on a listheader