Place after open

Author: liuzicheng1987

include/rfl/io/save_string.hpp

@@ -14,10 +14,10 @@ Result<Nothing> save_string(const std::string& _fname, const T& _obj,
                             const WriteFunction& _write) {
   try {
     std::ofstream outfile;
+    outfile.open(_fname);
     if (!outfile.is_open()) {
       return error("Unable to open file '" + _fname + "' for writing.");
     }
-    outfile.open(_fname);
     _write(_obj, outfile);
     outfile.close();
   } catch (std::exception& e) {