Mark destructors of several libraries as virtual.

src/Library/AttackLibrary.hpp

@@ -14,7 +14,7 @@ namespace CreatureLib::Library {
         AttackLibrary(size_t initialCapacity = 32)
             : _attacks(std::unordered_map<std::string, const AttackData*>(initialCapacity)){};
 
-        ~AttackLibrary() {
+        virtual ~AttackLibrary() {
             for (auto attack : _attacks) {
                 delete attack.second;
             }