fix null pointer dereference on non-linux
fix null pointer dereference on non-linux

ruo91/mdbm,ruo91/mdbm,eam/mdbm,eam/mdbm,yahoo/mdbm,timrc-git/mdbm,yahoo/mdbm,yahoo/mdbm,ruo91/mdbm,yahoo/mdbm,eam/mdbm,timrc-git/mdbm,ruo91/mdbm,eam/mdbm,timrc-git/mdbm,ruo91/mdbm,ruo91/mdbm,timrc-git/mdbm,eam/mdbm,ruo91/mdbm,yahoo/mdbm,yahoo/mdbm,yahoo/mdbm,timrc-git/mdbm,eam/mdbm,timrc-git/mdbm,eam/mdbm,timrc-git/mdbm