sdktool --qt '' still selects default Qt

sdktool addKit --qt '' ... produces an entry in profiles.xml with

    <value type="QString" key="QtSupport.QtInformation"></value>

Previously (in QtCreator 4.8.2) this worked as a kit with no Qt version selected.
But in 4.10.1, it seems to be selecting the default Qt, even when that Qt is not ABI-compatible with the toolchain in the kit.

If I manually edit a kit to say Qt version: "None" in the GUI, it writes

    <value type="int" key="QtSupport.QtInformation">-1</value>

which is thereafter left alone. But there does not seem to be a way to make sdktool create this.

I'm not sure whether sdktool should create the -1 like the GUI does, or the loading process should respect empty strings as it did before.