libtracker-data: Fix error handling for anonymous blank nodes
libtracker-data: Fix error handling for anonymous blank nodes

Errors occurring in inserts within anonymous blank nodes were not
propagated correctly.

hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker