Fix oob read terminating data with 0

Fix crash e3c41070342cf84dea077356ddbb8ebf4326a601

==12073==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6110000003bb at pc 0x0000004c234c bp 0x7fcf6359ec30 sp 0x7fcf6359e3
e0
READ of size 11 at 0x6110000003bb thread T0
    #0 0x4c234b in __interceptor_strlen.part.30 /home/alvaro/tools/llvm/llvm/projects/compiler-rt/lib/asan/../sanitizer_common/sanitize
r_common_interceptors.inc:301
    #1 0x7165e6579d87 in std::char_traits<char>::length(char const*) /build/gcc-multilib/src/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3
/include/bits/char_traits.h:269
    #2 0x7165e6579d87 in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std
::allocator<char> const&) /build/gcc-multilib/src/gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:495
    #3 0x5c3333 in ELFIO::elfio::load_sections(std::istream&) /home/alvaro/fuzzers/elfio/ELFIO/examples/libfuzzer/../../elfio/elfio.hpp
:413:44