plugins: lua: make sure lua_type_to_di_object doesn't pop the table
plugins: lua: make sure lua_type_to_di_object doesn't pop the table

caller to lua_type_to_di_object doesn't expect the function to alter the
elements on the stack, however luaL_ref does pop an element from the
stack, breaking the expectation.

This commit fixes that.

Signed-off-by: Yuxuan Shui <7f7e1535bcd10fa942d56a3436533af20f33203f@gmail.com>

yshui/deai,yshui/deai,yshui/deai