sidedata: make sure we don't use the flag if there are not sidedata

Ensuring this at this level seems safer than relying on caller doing the right
thing.



G: changed mercurial/revlog.py

Differential Revision: https://phab.mercurial-scm.org/D6895

mercurial/revlog.py

@@ -1861,6 +1861,7 b' class revlog(object):'
 
         if sidedata is None:
             sidedata = {}
+            flags = flags & ~REVIDX_SIDEDATA
         elif not self.hassidedata:
             raise error.ProgrammingError(
                 _("trying to add sidedata to a revlog who don't support them")