improve verification of invalid indexes on deque's elements access

[douglasfanucchi]

https://github.com/douglasfanucchi/data-structure-cpp/blob/6566b4c565923473f0d3b001248008029fb0fc2a/includes/Deque.hpp#L105C77-L105C79 is not enough to avoid "Conditional jump or move depends on uninitialized value"