Fixed bug in CachedSearchResult where the index file was retrieved even if it didn't exist. Added validation for empty or null tag filters.
Fixed bug in CachedSearchResult where the index file was retrieved even if it didn't exist. Added validation for empty or null tag filters.

wangtuanjie/kairosdb,pawellesniewski/kairosdb,rdettai/kairosdb,pawellesniewski/kairosdb,KCFTech/kairosdb,george-aprozeanu/kairosdb,rdettai/kairosdb,ppbizapps/kairosdb,panqingcui/kairosdb-1,KCFTech/kairosdb,ppbizapps/kairosdb,at15/kairosdb-1,deejay1/kairosdb,panqingcui/kairosdb-1,george-aprozeanu/kairosdb,kairosdb/kairosdb,deejay1/kairosdb,at15/kairosdb-1,deejay1/kairosdb,panqingcui/kairosdb-1,wangtuanjie/kairosdb,rdettai/kairosdb,at15/kairosdb-1,pawellesniewski/kairosdb,ppbizapps/kairosdb,KCFTech/kairosdb,george-aprozeanu/kairosdb,lgscofield/kairosdb,george-aprozeanu/kairosdb,lgscofield/kairosdb,KCFTech/kairosdb,kairosdb/kairosdb,KCFTech/kairosdb,at15/kairosdb-1,pawellesniewski/kairosdb,at15/kairosdb-1,wangtuanjie/kairosdb,deejay1/kairosdb,lgscofield/kairosdb,lgscofield/kairosdb,rdettai/kairosdb,ppbizapps/kairosdb,ppbizapps/kairosdb,rdettai/kairosdb,lgscofield/kairosdb,kairosdb/kairosdb,panqingcui/kairosdb-1,pawellesniewski/kairosdb,kairosdb/kairosdb,panqingcui/kairosdb-1,deejay1/kairosdb,wangtuanjie/kairosdb,kairosdb/kairosdb,george-aprozeanu/kairosdb,wangtuanjie/kairosdb,kairosdb/kairosdb