Follow up to r37520 -- we probably shouldn't convert an error return into a crash dump.
Follow up to r37520 -- we probably shouldn't convert an error return into
a crash dump.

[ oop: actually, prior to 37520, it returned "no diffs" for unversioned or
  non-existent nodes ]

* subversion/libsvn_wc/props.c:
  (svn_wc_get_prop_diffs): return an error if the specified node does not
    exist, rather than asserting it does.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@877771 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion