See the comment around line 990 of ra_dav/fetch.c. The underlying
property fetch systems are not properly seeing the 404 status for a
property, and attempting to return its value. This comes through the
system as an empty string.
Specifically, in props.c, we attempt to blend some XML parsing of the
response (to fetch the CDATA out of a property's DAV:href element) and
fetching raw values through Neon's property management (which *does*
respect the 404). The behaviors need to be sorted out and implemented
properly.