Fixed compile error

[philipp-classen]

Fixes the following compile error:

./src/util/labelanalysis.hpp: In function ‘void analyze_labels(std::__cxx11::string, int)’
./src/util/labelanalysis.hpp:169:14: error: no match for ‘operator==’ (operand types are ‘std::ofstream {aka std::basic_ofstream<char>}’ and ‘long int’)