CSM: Fix itemstack:get_meta() 'metadata' indexing error

src/script/cpp_api/s_security.cpp

@@ -243,6 +243,7 @@ void ScriptApiSecurity::initializeSecurityClient()
 		"rawset",
 		"select",
 		"setfenv",
+		// getmetatable can be used to escape the sandbox
 		"setmetatable",
 		"tonumber",
 		"tostring",

src/script/scripting_client.cpp

@@ -24,6 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "lua_api/l_client.h"
 #include "lua_api/l_env.h"
 #include "lua_api/l_item.h"
+#include "lua_api/l_itemstackmeta.h"
 #include "lua_api/l_minimap.h"
 #include "lua_api/l_modchannels.h"
 #include "lua_api/l_particles_local.h"
@@ -67,6 +68,7 @@ ClientScripting::ClientScripting(Client *client):
 void ClientScripting::InitializeModApi(lua_State *L, int top)
 {
 	LuaItemStack::Register(L);
+	ItemStackMetaRef::Register(L);
 	StorageRef::Register(L);
 	LuaMinimap::Register(L);
 	NodeMetaRef::RegisterClient(L);