Fix another Coverity error: key_len + 1 could overflow. So just bail if someone has an absurdly long key in their svn dir-prop-base.
Fix another Coverity error: key_len + 1 could overflow. So just bail if someone has an absurdly long key in their svn dir-prop-base.

ggreer/the_silver_searcher,msys2/the_silver_searcher,k-takata/the_silver_searcher,bhaak/the_silver_searcher,lizh06/the_silver_searcher,lizh06/the_silver_searcher,nodakai/the_silver_searcher,k-takata/the_silver_searcher,nodakai/the_silver_searcher,msys2/the_silver_searcher,k-takata/the_silver_searcher,sebgod/the_silver_searcher,avih/the_silver_searcher,JFLarvoire/the_silver_searcher,ggreer/the_silver_searcher,nodakai/the_silver_searcher,JFLarvoire/the_silver_searcher,godbyk/the_silver_searcher,nodakai/the_silver_searcher,godbyk/the_silver_searcher,lecheel/the_silver_searcher,godbyk/the_silver_searcher,JFLarvoire/the_silver_searcher,JFLarvoire/the_silver_searcher,bhaak/the_silver_searcher,bhaak/the_silver_searcher,sebgod/the_silver_searcher,lizh06/the_silver_searcher,msys2/the_silver_searcher,ggreer/the_silver_searcher,JFLarvoire/the_silver_searcher,avih/the_silver_searcher,avih/the_silver_searcher,godbyk/the_silver_searcher,msys2/the_silver_searcher,lecheel/the_silver_searcher,bhaak/the_silver_searcher,bhaak/the_silver_searcher,sebgod/the_silver_searcher,ggreer/the_silver_searcher,nodakai/the_silver_searcher,sebgod/the_silver_searcher,k-takata/the_silver_searcher,avih/the_silver_searcher,JFLarvoire/the_silver_searcher,lizh06/the_silver_searcher,lecheel/the_silver_searcher,godbyk/the_silver_searcher,avih/the_silver_searcher,JFLarvoire/the_silver_searcher,lecheel/the_silver_searcher,msys2/the_silver_searcher,k-takata/the_silver_searcher