This looks like a regression from #411 (https://sourceforge.net/p/wix/bugs/411/), which claims to have been resolved in 2005 (not sure which version that translates to). To restate #411 (https://sourceforge.net/p/wix/bugs/411/), if you try to use an empty Value attribute in an IniFile element, WiX complains that "error CNDL0006 : The IniFile/@Value attribute's value cannot be an empty string. If you want the value to be null or empty, simply remove the entire attribute." However, upon removing the entire attribute as suggested, WiX helpfully informs me that "error CNDL0010 : The IniFile/@Value attribute was not found; it is required."
It would be most excellent if WiX told me what I'm trying to do is impossible instead of giving false hope.
This was seen in WiX 3.5.2519.0