[i18n] fix build on macos

Signed-off-by: R4SAS <r4sas@i2pmail.org>

i18n/I18N.h

@@ -97,7 +97,7 @@ std::string tr (TValue&& arg, TArgs&&... args)
 	size_t size = std::snprintf(NULL, 0, tr_str.c_str(), std::forward<TArgs>(args)...);
 	size = size + 1;
 	std::string str(size, 0);
-	std::snprintf(str.data(), size, tr_str.c_str(), std::forward<TArgs>(args)...);
+	std::snprintf(&str.front(), size, tr_str.c_str(), std::forward<TArgs>(args)...);
 
 	return str;
 }
@@ -129,7 +129,7 @@ std::string ntr (TValue&& arg, TValue2&& arg2, int& n, TArgs&&... args)
 	size_t size = std::snprintf(NULL, 0, tr_str.c_str(), std::forward<TArgs>(args)...);
 	size = size + 1;
 	std::string str(size, 0);
-	std::snprintf(str.data(), size, tr_str.c_str(), std::forward<TArgs>(args)...);
+	std::snprintf(&str.front(), size, tr_str.c_str(), std::forward<TArgs>(args)...);
 
 	return str;
 }