a tiny memory leak in virgo_exec.c found by clang-checker
in virgo_lua_debugger.c: when tmp is NULL, tmp->next results in dereferencing NULL pointer
Merge branch 'master' into fixes/detected_by_clang-checker
Merge pull request #1 from virgo-agent-toolkit/fixes/detected_by_clang-checker

bugs detected by clang checker
upgrade tweaks