QFormLayout ASSERTs when verticalSpacing is not set

Using QFormLayout, we run into reproducible crashes with Form layouts.

A workaround is to add the verticalSpacing property to the Formlayout. With default settings of QFormlayout, it ASSERTs:

Designer(16229)/default qt_assert: ASSERT: "uniformSpacer >= 0 || spacing >= 0" in file ../../include/QtWidgets/5.2.0/QtWidgets/private/../../../../../src/widgets/kernel/qlayoutengine_p.h, line 78

Adding the following to the ui file makes the formlayout work as expected:

<property name="verticalSpacing">
<number>0</number>
</property>

Attached files:

• good example (doesn't crash, works)
• bad example (crashes when opening in designer)
• backtrace

This is using master built on Friday.