CalDav Servers usually return relative URLs to Events in their
multistatus responses. KDAV up to now converted them into absolute URLs
when creating followup "calendar-multiget" request. It seems that some
server implemenations can't cope with that behavior and return and empty
result set for such queries.
Note: As this changes the format of the "remoteid" this requires and
addtional small fix in kdepim-runtime
Partially fixes: https://bugs.kde.org/show_bug.cgi?id=386985