Blender Git Loki

Fix failing "Edit Source" (asserts) while number slider was visible

E.g. steps to reproduce:
* Enter Vertex Paint mode
* In the tool settings, right-click > "Edit Source"

When creating a number slider via `layout.prop(..., slider=True)`, the UI code
would reallocate the number button to be a number-slider button. That's because
we now actually have different button data-structures for these (see
e6f0b60c2e911). The edit source code stored data based on the button pointers,
which didn't get updated after changing the type. The fix just adds this
updating.