Open the attached bug doc. It contains a small DOM instance of the form
<level1>
  <level2 attribute="some value"/>
</level1>

Additionally, it contains a text field control which is bound to the
second-level element.

- open the property browser for this control on the tab page "Data"
- click the "..." button behind the "Binding expression" property
=> the expression builder dialog opens.
Note that the "Condition" properly displays "level1/level2", but the "Result"
field is (unexpectedly) empty
- enter "." in the "Condition" field
=> the result displays the "level2" element.

White this is expected for other properties (e.g. "Relevant"), it does not make
sense for the "Binding expression". The reason is that the other properties are
relative (if possible) to the node addressed by the binding expression, but the
binding expression is always absolute. That is, if you would enter "level1" as
expression, it's expected to display the "level1" element. Instead, currently
nothing is displayed in this case, since "level1" is evaluated relative to the
current binding expression (which was active before the dialog was opened),
which is "level1/level2".