Fix X360 Crossplay (#26)

^Reviewed-on: pieeebot/cafeberry#26

Co-authored-by: qloak <realminecart@gmail.com>

Minecraft.Client/PS3/Leaderboards/base64.h

@@ -2,6 +2,6 @@
 
 #include <string>
 
-std::string base64_encode(std::string str);
+std::string base64_encode(const std::string& str);
 std::string base64_encode(unsigned char const* , unsigned int len);
 std::string base64_decode(std::string const& s);