Fix issue #431:
Fix issue #431:

(delta_proplists): Pass null value to delete a property.  Also, check
for trivial case first, though this is only a performance enhancement
and doesn't affect behavior.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@839924 13f79535-47bb-0310-9956-ffa450edef68

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